U.S. patent application number 09/754426 was filed with the patent office on 2001-09-13 for porous surface compositions and methods of retaining biological samples on said surface.
Invention is credited to Brown, James F..
Application Number | 20010021726 09/754426 |
Document ID | / |
Family ID | 25445991 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010021726 |
Kind Code |
A1 |
Brown, James F. |
September 13, 2001 |
Porous surface compositions and methods of retaining biological
samples on said surface
Abstract
A coating formulation for making a porous coating on a
laboratory apparatus is provided. The formulation comprises 100
parts by weight hardenable resinous material, and from about 0.1 to
about 50 parts by weight blowing agent based on the 100 parts by
weight resinous material. The resinous material has a hardening
time which is sufficiently short such that gas generated by the
blowing agent is entrapped within the resinous material. The
coating formulation is hardenable upon application to a surface of
a laboratory apparatus to form a porous coating which is used for
marking purposes or for the retention of biological samples.
Methods of retaining a biological sample on a coated laboratory
apparatus having a surface made of the coating formulation are also
provided.
Inventors: |
Brown, James F.; (Clifton,
VA) |
Correspondence
Address: |
Leonard D. Bowersox, Esq.
KILYK & BOWERSOX, P.L.L.C.
3603-E Chain Bridge Road
Fairfax
VA
22030
US
|
Family ID: |
25445991 |
Appl. No.: |
09/754426 |
Filed: |
January 4, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09754426 |
Jan 4, 2001 |
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09417594 |
Oct 14, 1999 |
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09417594 |
Oct 14, 1999 |
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08921796 |
Sep 2, 1997 |
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5989692 |
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Current U.S.
Class: |
521/82 ; 521/155;
521/178 |
Current CPC
Class: |
Y10T 428/24967 20150115;
C08G 59/4021 20130101; B01L 99/00 20130101; Y10T 428/249953
20150401; C03C 2217/445 20130101; C09D 7/00 20130101; C03C 17/007
20130101; C03C 2217/485 20130101; C03C 2217/425 20130101 |
Class at
Publication: |
521/82 ; 521/155;
521/178 |
International
Class: |
C08J 009/00 |
Claims
What is claimed is:
1. A coating formulation for making a hard porous coating on a
laboratory apparatus, said formulation comprising 100 parts by
weight hardenable resinous material, and from about 0.1 part by
weight to about 50 parts by weight blowing agent based on the 100
parts by weight resinous material, said blowing agent capable of
generating gas under conditions for hardening said resinous
material, said resinous material having a hardening time
sufficiently short to entrap gas generated by said blowing agent
and prevent release of substantially all gas generated upon
activation of said blowing agent, wherein said formulation is
hardenable upon application to a surface of a laboratory apparatus
to form a porous coating which is scratch resistant to a #4
pencil.
2. A coating formulation as claimed in claim 1 wherein said
formulation is hardenable to form a porous coating that is scratch
resistant to a #8 pencil.
3. A coating formulation as claimed in claim 1 wherein said
formulation is hardenable upon application to a surface of a
laboratory apparatus to form a porous coating which retains a
marking material and is substantially chemically resistant to
sodium hydroxide solutions and boiling water.
4. A coating formulation as claimed in claim 1 wherein said
hardenable resinous material is curable and further comprises an
amount of curing agent effective to cure and harden said resinous
material.
5. A coating formulation as claimed in claim 4 wherein said
resinous material comprises a curable novolac epoxy resin and said
curing agent comprises dicyandiamide.
6. A coating formulation as claimed in claim 1 wherein said
resinous material comprises a curable urethane resin.
7. A coating formulation as claimed in claim 1 wherein said
resinous material comprises an unsaturated resinous material.
8. A coating formulation as claimed in claim 1 wherein said blowing
agent comprises a fluorinated liquid.
9. A coating formulation as claimed in claim 1 further comprising
an effective amount of adhesion promoter material to substantially
improve adhesion of the hardenable resinous material to a surface
of a laboratory apparatus.
10. A coating formulation as claimed in claim 1 further comprising
an effective amount of solvent to render the viscosity of the
formulation sufficiently thin for enabling application by at least
one technique selected from the group consisting of screen printing
techniques, ink jet printing techniques, and pad printing
techniques.
11. A coating formulation as claimed in claim 1 further comprising
an effective amount of dispersing agent to substantially improve
homogeneous dispersion of said blowing agent throughout said
resinous material.
12. A coating formulation as claimed in claim 1 further comprising
up to 300 parts by weight pigment based on the 100 parts by weight
resinous material.
13. A method of retaining a biological sample for analysis thereof,
said method comprising applying a biological sample to a porous
surface of a laboratory apparatus which retains said sample, said
porous surface comprising the hardened product of a coating
formulation applied to said laboratory apparatus, said coating
formulation comprising 100 parts by weight hardenable resinous
material, and from about 0.1 to about 50 parts by weight blowing
agent based on the 100 parts by weight resinous material, said
blowing agent being dispersed throughout said hardened resinous
material, said hardened product comprising a porous surface,
hardened resinous material, and gas cells generated by said blowing
agent, said gas cells forming a network of cellular voids
throughout the resinous material at the surface of the coating.
14. The method of claim 13, wherein said porous surface is scratch
resistant to a #8 pencil.
15. The method of claim 13, wherein said porous coating is
substantially chemically resistant to sodium hydroxide solutions
and boiling water.
16. The method of claim 13, wherein said hardenable resinous
material comprises a curable novolac epoxy resin and said curing
agent comprises dicyandiamide.
17. The method of claim 13, wherein said resinous material
comprises a curable urethane resin.
18. The method of claim 13, wherein said resinous material
comprises an unsaturated resinous material.
19. The method of claim 13, wherein said blowing agent comprises a
fluorinated material.
20. The method of claim 13, wherein said coating formulation
comprises pigment present in an amount of up to about 300 parts by
weight based on 100 parts by weight said resinous material.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional of U.S. patent
application Ser. No. 08/921,796 filed Sep. 2, 1997, now U.S. Pat.
No. ______, issued ______.
FIELD OF THE INVENTION
[0002] The present invention relates to compositions useful for
forming porous surfaces on articles, particularly on laboratory
apparatus including microscope slides and vessels for handling,
measuring, reacting, incubating, containing, storing, restraining,
isolating and transporting biological samples. The present
invention also relates to a method of retaining a biological sample
on said surface for the observation and analysis of the sample.
BACKGROUND OF THE INVENTION
[0003] Laboratory apparatus including microscope slides, microtiter
plates, vials, flasks, test tubes, syringes, coverslips, films and
porous substrates, and assemblies comprising such devices, are
often used to handle, measure, react, incubate, contain, store,
restrain, isolate and transport important and sometimes minute
volumes of liquid, particularly biological samples. Often there is
a need to mark the apparatus to prevent confusion among samples
when working with multiple samples. Accordingly, there is a need
for a marking surface on a laboratory apparatus.
[0004] It is well known to frost a portion of the surface of a
laboratory apparatus to form a marking surface. The frosted area is
created by sandblasting, acid etching, mechanical abrading, or
other methods of roughening the surface of the apparatus to create
a surface which may be marked with a pen, pencil, or other marking
instrument. Despite the matte finish of a roughened marking
surface, permanent marking of the apparatus is nonetheless not
assured.
[0005] The aforementioned techniques create a frosted surface by
removing material from the apparatus surface, which necessarily
results in a marking surface which is recessed from, or no higher
than, the surface of the apparatus. The marking surface therefore
does not provide a means of spacing stacked flat apparatus, for
example, microscope slides. In addition, the marking surface is not
provided with a pronounced background to contrast with marking
material marked thereon.
[0006] Coating formulations which can be applied to a laboratory
apparatus to form a marking surface are also known. A raised
marking surface for a microscope slide is disclosed in U.S. Pat.
No. 4,481,246 to Melisz et al. This patent discloses a resin-based
coating having a sufficient amount of granular medium to impart
porosity to the coating. To impart porosity, however, very high
loadings of the granular medium are required; otherwise, the liquid
epoxy in the formulation engulfs the granular medium and forms a
smooth non-porous texture at the exposed surface of the coating.
The high loadings of granular medium require the formulation to be
highly viscous and have a limited range of Theological properties.
Heavily loaded coatings are weakened or embrittled by the presence
of large amounts of clay or pigment, and the permanence of a
marking material applied to the surface may be compromised by
marking and handling the coating. Furthermore, because so much of
the coating formulation comprises granular medium, the chemical
resistance afforded by the epoxy resin is diminished relative to
the chemical resistance afforded by a coating comprising more
substantial amounts of resinous material. Coatings which are
believed to be made in accordance with the teachings of U.S. Pat.
No. 4,481,246 to Melisz et al. are not chemically resistant to
sodium hydroxide solutions and are measurably weakened by exposure
to hydrochloric acid solutions in ethanol, boiling deionized water,
xylene, and ethanol. In addition, coatings made in accordance with
the patent may chalk, that is, the surface may break down to a
powder upon contact with a marking instrument, which is especially
undesirable in surfaces for identifying a sample or retaining a
biological sample.
[0007] The surfaces of laboratory apparatus, for example, petri
dishes, microscope slides and microtiter plates are often treated
to enable the growth, manipulation and maintenance of cell
cultures. These superficial treatments include exposure of plastic
surfaces to electromagnetically generated plasmas using various
gases or exposure of glass surfaces to silanizing liquids and
gases. Often, the aforementioned exposure steps are followed by the
application of coatings of extracellular matrix proteins. Cell
types have been coated to a surface of a laboratory apparatus and
maintained and/or grown by the effusion of nutrients and cell
factors to their attached surfaces. Some cell types benefit from a
cavernous or cave-like topology.
[0008] Superficial, and generally monomolecular treatments of
laboratory apparatus to provide cell growth surfaces do not allow
the effusion of nutrients or cell factors at their interface with
cells, nor do they have a porous topology. It is desirable to
provide a coating for a laboratory apparatus that allows the
effusion of nutrients or cell factors at the interface of the
coating and cells, and which has a porous topology.
[0009] There is a need for an even more permanent marking surface
for laboratory apparatus, and for a formulation that provides more
permanence and better Theological properties including thixotropy
and viscosity. There is a need for a coating formulation that can
be applied by a pad printing technique to provide a marking
surface. There is a need for a coating formulation that can be
printed onto a laboratory apparatus to form a biological
sample-retaining coating useful for growing and analyzing a
biological sample. There is also a need for a permanent coating
material for laboratory apparatus which can promote the growth,
life, maintenance or preservation of a biological sample.
[0010] The present invention provides a formulation which can be
applied to a laboratory apparatus and dried or cured to form a
coating having a porous surface. The present invention also
provides a laboratory apparatus having a porous surface which can
be used as a marking surface for substantially permanent marking
applications. The present invention also provides a laboratory
apparatus having a porous coating which can be used for retaining a
biological sample.
SUMMARY OF THE INVENTION
[0011] The present invention relates to a coating formulation for
forming porous surfaces on laboratory apparatus. According to
embodiments of the invention, a coating formulation is provided
comprising a hardenable resinous material and a blowing agent. The
material and agent selected, and the relative amounts of each, are
provided such that the formulation can be applied to a laboratory
apparatus and hardened by curing, drying or cooling to provide a
hard coating having a porous surface. The present invention also
provides a laboratory apparatus having a porous surface useful as a
permanent marking surface. The present invention also provides a
laboratory apparatus having a porous surface useful for retaining a
biological sample. Coatings according to embodiments of the present
invention exhibit excellent weatherability, chemical resistance,
adhesion, low shrinkage, heat resistance, abrasion resistance,
impact strength, and water resistance, and do not chalk or form
powders when marked upon.
[0012] According to embodiments of the invention, a coating
formulation is provided comprising 100 parts by weight resinous
material, from about 0.1 to about 50 parts by weight blowing agent,
from 0 to about 500 parts by weight solvent for the resinous
material, from 0 to about 100 parts by weight resinous material
curing agent, from 0 to about 5 parts by weight adhesion promoting
material, from 0 to about 300 parts by weight pigment, and from 0
to about 50 parts by weight dispersing agent.
[0013] The resinous material preferably has a fast hardening time
or fast cure response. Preferably, the resinous material cures or
dries very quickly so that gas-generated by the formulation during
curing or drying of the resinous material can be entrapped within
the hardened resinous material. Preferably, the resinous material
cures or dries fast enough so that gas-generated by the coating
formulation does not completely escape from the resinous material
before the material is substantially cured or dried. Exemplary
resinous materials include ultraviolet-curable and/or curable epoxy
resins.
[0014] The blowing agent, or gas-generating agent, preferably forms
a gas which is insoluble under the hardening conditions of the
resinous material. As gas bubbles are formed during curing or
hardening of the resinous material, the bubbles migrate toward the
upper surface of the coating due to gravity. As some of the bubbles
pop or are broken at the upper surface of the coating, they form
openings or pores at the surface resulting in a porous surface.
[0015] As the blowing agent generates gas, the resulting gas
bubbles form a network of cellular voids throughout the resinous
material, at least at the surface of the coating. According to
embodiments of the invention, the coating formulation forms a
microporous foam state wherein at least the operational exposed
surface of a coating made from the formulation is at least
partially foamed and porous.
[0016] According to embodiments of the invention, the coating
formulation forms a hard foam upon drying or curing, and provides a
porous surface which is excellent for permanently retaining marking
materials and/or for retaining biological samples for analysis.
According to some embodiments of the invention, the porous surface
may preferably be hydrophilic so as to readily absorb and retain
many marking formulations including water-based inks. According to
embodiments of the invention, the surface energy or surface
chemistry of the porous surface may be adjusted using selected
resins, co-resins or surface-active agents to best accommodate
marking materials. The surface openings or pores enable
penetration, absorption, capillary force holding and retention of
marking material applied to the coating.
[0017] According to some embodiments of the invention, the openings
or pores formed from gas bubbles generated within the coating
formulation form an excellent retention mechanism for the
manipulation and retention of a biological sample. As a cell growth
apparatus, the coating may be applied to an apparatus surface, for
example, the surface of a microscope slide, and loaded with sample.
The sample can then be retained in the porous coating and observed
over a period of time. According to some embodiments of the
invention, a retained biological sample loaded into the porous
surface may be maintained with nutrients and air over a period of
time, and thus the growth and development of biological material,
for example, a cell culture may be observed and analyzed. According
to embodiments of the invention, the surface energy or surface
chemistry of the porous surface may be adjusted using selected
resins, co-resins or surface-active agents to best facilitate cell
growth.
[0018] According to embodiments of the invention, the viscosity of
the coating formulations may be adjusted by addition of solvents.
Other optional additives may also be included in the coating
formulation according to embodiments of the invention. In addition
to solvents, other additives including flow control agents,
leveling agents, and surfactants may be incorporated to improve the
printability or applicability of the coating formulation, and/or to
improve the texture, appearance or permanent markability of the
hardened porous coating.
DETAILED DESCRIPTION OF THE INVENTION
[0019] According to embodiments of the present invention, apparatus
for handling, measuring, reacting, incubating, containing, storing,
restraining, isolating and transporting liquids are coated with a
coating formulation which includes a gas-generating agent and a
resinous material. The resinous material cures, dries or otherwise
hardens sufficiently quickly to entrap gas bubbles generated by the
gas-generating agent. The cured or dried hardened coating exhibits
a porous surface, formed by the gas bubbles, at the surface of the
coating. The porous surface is excellent for marking applications
and can be formulated to readily and permanently accept many
marking mediums including inks and pencil. The porous foamed
coatings are also chemically resistant, more so than porous
non-foamed coatings which attribute porosity to a sufficient amount
of granular medium.
[0020] According to embodiments of the invention, the coating
formulation is applied to a laboratory apparatus at a thickness
sufficient to form a markable surface. Because a markable surface
may be obtained from a very thin coating, coating thicknesses of
less than about 100 mils may be used, for example, thicknesses of
less than about 2 mils. According to some preferred embodiments of
the invention, coating thickness of less than or equal to about 1
mil are provided.
[0021] Particular laboratory apparatus which can be coated
according to the present invention include microscope slides,
microscope slide assemblies, microscope slide coverslips, petri
dishes, vials, flasks, test tubes, syringes, sample chambers for
analytical devices, tapes, laminates, plates, arrays, tubing, and
devices and apparatus with operational surfaces comprising plastic,
sintered materials, semiconductors, glass, ceramic, metal and
primed or pre-coated surfaces. The invention may also be used on
operational surfaces which are porous, smooth, rough, pitted,
grooved, cross-hatched, striated, or patterned with physical
features.
[0022] According to some embodiments of the invention, a coating
formulation is provided having a porous surface which provides an
excellent retention mechanism for the manipulation and retention of
a biological sample. As a cell growth apparatus, the coating may be
applied to an apparatus surface, for example, the surface of a
microscope slide, and loaded with sample. The sample can then be
retained in the porous coating and observed over a period of time.
According to some embodiments of the invention, a retained
biological sample loaded into the porous surface may be maintained
with nutrients and air over a period of time, and thus the growth
and development of biological material, for example, biological
material comprising a cell culture, may be observed and
analyzed.
[0023] According to some embodiments of the invention, the
laboratory apparatus comprises a microscope slide or other
substantially flat device having an operational surface at least
partially coated with a coating formulation according to the
invention. The porous coating may be used to retain, contain or
isolate a biological sample and is particularly useful as a cell
growth surface for the development, growth, life or preservation of
a biological sample. A biological sample can thus be isolated on
and in the porous surface and subjected to chemical and biological
reactions.
[0024] According to embodiments of the invention, the porous
coating is scratch-resistant to a #4 pencil. According to some
embodiments of the invention, the porous coating is
scratch-resistant to a #6 pencil. According to some preferred
embodiments of the invention, the porous coating is
scratch-resistant to a #8 pencil.
[0025] According to embodiments of the invention, a coating
formulation is provided comprising 100 parts by weight hardenable
resinous material, from about 0.1 to about 50 parts by weight
blowing agent, from 0 to about 500 parts by weight solvent for the
resinous material, from 0 to about 100 parts by weight curing
agent, from 0 to about 5 parts by weight adhesion promoting
material, from 0 to about 300 parts by weight pigment, and from 0
to about 50 parts by weight dispersing agent.
[0026] According to embodiments of the invention, the resinous
material may comprise at least one material selected from the group
consisting of curable resinous materials, resinous materials that
harden upon drying, and dry-melt resinous materials. Exemplary of
curable-resins are ultraviolet-curable, photo-curable, 2-part
curable, moisture curable, catalyst curable, and heat-curable
resins. Exemplary of photo-curable resins are polymerizable
acrylates. Exemplary of resinous materials that harden upon drying
include water-soluble resins, epoxy resins, urethanes, silicones,
acrylics, latexes, polyesters and cellulosics. Exemplary of
dry-melt resinous materials are polyethylene and other
thermosetting or thermoplastic resins. Curable resins, and resins
that harden upon drying, are preferred for the resinous material
according to embodiments of the invention.
[0027] According to embodiments of the invention, the resinous
material is formed into a cellular polymer. According to
embodiments of the invention, the resinous material may comprise
one or more at least partially foamable polymer selected from the
group consisting of epoxy resins, urethane monomers and/or polymers
including curable urethane resins, cellulose acetate, phenolic
resin, polyethylene, polystyrene, silicones, urea-formaldehyde
resins, latex foam rubbers, natural rubbers, synthetic elastomers,
poly(vinyl chloride), ebonite, polytetrafluoroethylene, and the
cellular polymers set forth at pages 118-121 of Concise
Encyclopedia of Polymer Science and Engineering, Kroschwitz
(Executive Editor), John Wiley & Sons, Inc. (1990), which is
herein incorporated by reference in its entirety.
[0028] According to embodiments of the invention, the resinous
material may comprise an unsaturated resin, that is, a resin which
comprises a component having a double bond, for example, an
ethylenically unsaturated component, or a component having a triple
bond, for example, a component having an isocyanate bond.
[0029] According to embodiments of the invention, the resinous
material may comprise a UV-curable, visible light-curable or
heat-curable resin. Other hardenable resins which may be used
include polymerizable acrylate resins, for example, the urethane
acrylate oligomer resins set forth in the SARTOMER Products Catalog
(pp. 28-29, 1997) which is herein incorporated by reference in its
entirety. The SARTOMER urethane acrylate resin CN 980 is preferred.
The urethane acrylates disclosed at pages 28-29 of the SARTOMER
Products Catalog generally exhibit excellent weatherability,
chemical resistance, adhesion, low shrinkage, heat resistance,
abrasion resistance, impact strength, and water resistance. These
properties make the urethane acrylate resins particularly preferred
resinous materials.
[0030] According to embodiments of the invention, a curable
acrylate resin is used as the resinous material and a curing agent
is present. The curing agent may preferably comprise a
photoinitiator.
[0031] Exemplary photoinitiators for acrylates include the ESACURE
and BP photoinitiators set forth on pages 40 and 41 of the SARTOMER
Product Catalog (1997), which is also incorporated herein by
reference, in its entirety. A preferred photoinitiator to be used
with a urethane acrylate is the SARTOMER photoinitiator ESACURE
KIP100F--a clear yellow liquid comprising alpha hydroxy ketone.
ESACURE KIP100F is a preferred photoinitiator for the SARTOMER
urethane acrylate CN 980,
[0032] According to embodiments of the invention, epoxy resins
including novolac epoxy resins may be used as the resinous
material. Epoxides comprising cycloaliphatic and diglycidyl ether
of Bisphenol A (DGEBA), for example, may be used. FX-512 may be
used as an epoxy catalyst according to embodiments of the
invention. FX-512 is described in the 3M Industrial Chemical
Products Division Product Information Bulletin UV Activated Epoxy
Curative FX-512 (1986), which is herein incorporated by reference
in its entirety. Wetting and leveling agents may be used according
to some embodiments of the invention wherein an epoxy resin is the
resinous material. Wetting and leveling agents which may be used
include FLUORAD FC-171 and FC-430 fluorochemical surfactants
available from 3M Industrial Chemical Products Division, St. Paul,
Minn.
[0033] According to embodiments of the invention, an epoxy resin
comprising trimethylol propane triglycidyl ether is used as the
resinous material, for example, ERISYS GE 30, available from CVC
Specialty Chemicals, Inc, Cherry Hill, N.J.
[0034] Another preferred class of resinous materials is the class
of D.E.N. epoxy novolac resins identified as D.E.N. 431, D.E.N.
438, D.E.N. 438-A85, D.E.N. 438-EK85, D.E.N. 438-MK75, D.E.N. 439,
D.E.N. 439-EK85, and D.E.N. 485, available from Eastech Chemical,
Inc., Philadelphia, Pa., and described in the Dow Chemical U.S.A.
bulletin D.E.N. Epoxy Novolac Resins Product Specification Guide
(1982). According to embodiments of the invention, the epoxy resins
D.E.N. 438, D.E.N. 438-EK85, D.E.N. 438-MK75, D.E.N. 439 and D.E.N.
439-EK85 are preferred resins for the resinous material. According
to embodiments of the invention, the epoxy resins D.E.N. 438,
D.E.N. 439, and D.E.N. 439-EK85 are more preferred resins for the
resinous material.
[0035] Optical and electronic adhesives which may be used as the
resinous material include the NORLAND adhesives set forth in the
publication of Norland Products, Inc., Norland UV Curing Adhesives,
which is incorporated herein by reference in its entirety. NORLAND
adhesives which may be used according to embodiments of the
invention include adhesives comprising a urethane, an acrylic or a
mercapto ester. The adhesives include the UV curable Norland
adhesives NOA 60, NOA 61, NOA 63, NOA 65, NOA 68, NOA 71, NOA 73,
NOA 81, NOA 88 and UVS 91, the UV/heat-curable adhesives NOA 83H,
NEA 121 and NEA 123, the UV/vis-curable adhesives NOA 72, and the
heat-curable adhesive NEA 155. Norland NOA 81 is a preferred
UV-curable adhesive for use as the resinous material.
[0036] According to embodiments of the invention, the
gas-generating agent, also referred to as a blowing agent or a
foaming agent, produces gas and may be used to generate cells (gas
pockets) in the resinous material. The gas-generating agents used
according to embodiments of the invention may be classified as
either physical or chemical blowing agents. Herein, the term
"gas-generating agent" is to be understood as including physical
and chemical blowing agents, including physical blowing agents
which generate gas upon boiling. According to embodiments of the
invention, a gas-generating agent is preferably selected which can
provide (1) long-term storage stability under fairly ordinary
conditions, (2) gas release over a controlled time and temperature
range, (3) low toxicity, odor, and color in both the agent itself
and in its decomposition products, (4) no deleterious effects on
the stability and processing characteristics of the polymer, (5)
the ability to produce cells of uniform size, (6) The ability to
produce stable foam, that is, a foam wherein gas is not lost from
the cell causing it to collapse, and (7) good cost-performance
relation and availability.
[0037] According to embodiments of the invention, the
gas-generating agent is a physical blowing agent which creates gas
by a phase change, for example, a liquid may be volatilized, or a
gas dissolved in a polymer under high pressure may be desorbed by
decompression. Chemical blowing agents which may be used according
to embodiments of the present invention produce gas by thermal
decomposition and, in a few instances, via a chemical reaction with
other components of the polymer system. A discussion of blowing
agents is found at pages 89-90 of Concise Encyclopedia of Polymer
Science and Engineering, Kroschwitz (Executive Editor), John Wiley
& Sons, Inc. (1990), which is herein incorporated by reference
in its entirety.
[0038] The gas generating agent may be a physical blowing agent
comprising at least one of n-pentane, 2,2-dimethylpropane,
1-pentene, n-hexane, 2-methylpentane, 3-methylpentane,
2,2-dimethylbutane, cyclohexane, n-heptane, 2,2-dimethyl pentane,
2,4-dimethylpentane, 3-ethylpentane, 1-heptene, toluene,
trichloromethane, tetrachloromethane, trichlorofluoromethane,
methanol, 2-propanol, isopropyl ether, methyl ethyl ketone, and
fluorinated hydrocarbon solvents.
[0039] According to embodiments of the invention, the
gas-generating agent may comprise fluorinated liquids, for example,
fluorinated organic liquids as disclosed in the product bulletin
1994 Fluorinert Liquids, available from 3M Specialty Chemicals,
West Caldwell, N.J. FLUORINERT liquids that may be used according
to the present invention include FC-84, FC-77, FC-104, FC-75,
FC-40, FC-43, FC-70, FC-71 FC-5312, FC-5320, FC-5350. According to
embodiments of the invention, the FLUORINERT liquids FC-40. FC-43,
FC-70, FC-71, FC-5312, FC-5320, and FC-5350 are preferred
gas-generating agents. According to embodiments of the invention,
the FLUORINERT liquids FC-70, FC-71 and FC-5312 are more preferred
gas-generating agents. The foregoing and other FLUORINERT liquids
are disclosed, for example, in the aforementioned 1994
Fluoriner.TM. Liquids product information bulletin and in the
Fluorinert.TM. Electronic Liquids 1989 Product Information bulletin
available from 3M Industrial Chemical Products Division, St. Paul,
Minn. Other fluorinated solvents which may be used include
Vertrel.RTM. XF (C.sub.5H.sub.2F.sub.10) or Freon TF, both
available from DuPont, Wilmington, Del., or the fluorinated
polyethers HT70, HT85, HT90, HT100, HT110, HT135, HT200, HT230,
HT250, HT260 and HT270, and the perfluorinated polyethers sold as
GALDEN, all from Ausimont USA, Inc. The Ausimont USA, Inc. solvent
designations indicate the boiling point of each solvent. Higher
boiling solvents, for example, HT250, HT260 and HT270, require more
heat to volatilize than coatings made with the lower boiling
solvents. The lower boiling Ausimont USA, Inc. solvents, for
example, HT70, more rapidly evaporate when compared to the higher
boiling solvents. AUSIMONT HT260 is a preferred fluorinated solvent
to use as a physical blowing agent according to embodiments of the
invention.
[0040] Other fluorocarbon solvents may be used as physical blowing
agents, and preferably have boiling ranges of from about 30.degree.
C. to about 250.degree. C. At least partially fluorinated solvents
are preferred for physical blowing agents, particularly those
fluorocarbon solvents having at least about 20% by weight fluorine
atoms per molecule.
[0041] According to some embodiments of the invention, the
gas-generating agent may be a chemical blowing agent and may
comprise, for example, an azide composition which releases nitrogen
gas (N.sub.2) upon activation, sodium bicarbonate NaHCO.sub.3 which
release CO.sub.2 upon activation. Other chemical blowing agents
which may be used according to embodiments of the invention include
dinitrosopenta-methylenetetramine, sulfonyl hydrazides,
azodicarbonamide, p-toluenesulfonyl semicarbazide,
5-phenyltetrazole, diisopropylhydrazodicarboxylate,
5-phenyl-3,6-dihydro-1,3,4-oxadiazine-2-one, and sodium
borohydride.
[0042] According to embodiments of the invention, the
gas-generating agent is compatible with the resinous material. The
gas-generating agent should preferably generate gas under the
conditions necessary to harden the resinous material. Therefore, if
a heat-curable resinous material is used, the gas-generating agent
should generate gas at about the temperature required for
heat-curing the material. If a resinous material that hardens upon
drying is used, the gas-generating agent should not require heat to
generate gas. If a UV-curable resinous material is used, the
gas-generating agent is preferably UV-activated.
[0043] According to embodiments of the invention, the
gas-generating agent is preferably compatible with the resinous
material such that a homogenous mixture of the two components may
be achieved, enabling a uniformly porous surface on a coating made
from the formulation.
[0044] According to embodiments of the invention, the
gas-generating agent is used in an amount effective to generate
sufficient gas to provide a cellular foamed polymer. The
gas-generating agent may be present in an amount of from about 0.1
to about 50 parts by weight based upon 100 parts by weight of the
resinous material. According to embodiments of the invention, the
gas-generating agent may be present in an amount of from about 0.5
to about 20 parts by weight, for example, from about 1 to about 5
parts by weight based upon 100 parts by weight of the resinous
material.
[0045] As the blowing agent generates gas, the resulting gas
bubbles form a network of cellular voids throughout the resinous
material, at least at the surface of the coating. According to
embodiments of the invention, the coating formulation forms a
microporous foam state wherein at least the operational exposed
surface of a coating made from the formulation is at least
partially foamed and porous. According to embodiments of the
invention, the coating formulation forms a hard foam upon drying or
curing, and provides a porous surface. The pores formed according
to some preferred embodiments of the invention are microporous.
According to some embodiments of the invention, the pores may have
an average pore size of from about 0.1 to about 10 microns in at
least one dimension, for example, from about 0.5 to about 3
microns.
[0046] In embodiments wherein a fluorocarbon liquid is used as a
physical blowing agent, the agent may form vertical tunnels
extending to the surface of the hardened coating. According to
embodiments of the invention, pores comprising vertical tunnels
having lengths of up to about 25 microns may be provided. These
"worm hole" tunnels may be achieved by using a fluorinated liquid
as a blowing agent, and are preferred due to the excellent
capillary forces the tunnels exert on a liquid marking material
applied to the porous surface of the coating. Some chemical blowing
agents including sodium bicarbonate may be used to form more
spherically-shaped pores as opposed to the tunnel-shaped pores
achieved with fluorinated physical blowing agents.
[0047] According to embodiments of the invention, the formulation
may comprise an adhesion promoter. If present, an adhesion promoter
may promote adhesion between a coating made from the formulation
and the surface of a laboratory apparatus. Exemplary of adhesion
promoters are glycidoxysilanes, including
3-glycidoxypropyl-trimethoxysilane. An exemplary
gamma-glycidoxypropyltrimethoxy-silane is available from Union
Carbide as Silicone A-187.
[0048] Coupling agents may also be used as adhesion promoting
monomers. Exemplary coupling agents include vinyltrimethoxysilane,
chloropropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane,
and 3-methacryloxypropyl-trimethoxysilane. Such silanes and
coupling agents, if present, can be present in amounts of from
about 1 part by weight to about 10 parts by weight, more preferably
from about 2 parts by weight to about 5 parts by weight, based on
100 parts by weight of resinous material.
[0049] Linkage mechanisms for binding the resinous material of the
present coating formulations to an operational surface of a
laboratory apparatus may be incorporated with the resinous material
and include functional linkage groups such as peroxide catalyzed
linkages, azo catalyzed linkages, free radical induced linkages,
cationically induced linkages, radiation induced linkages, vinyl
linkages, methacrylate linkages, urethane linkages, epoxy linkages,
silane linkages, and siloxane linkages.
[0050] Other adhesion promoting monomers can be added to the
coating formulations of the invention. If used, adhesion promoting
monomers other than silanes may preferably be used in amounts of
from about 1% by weight to about 40% by weight, more preferably
from about 5% by weight to about 20% by weight, based on the weight
of the polymerization product making up the coating material.
Adhesion promoting monomers which may be used include alkoxy
terminated monomers and methacrylate esters and acrylate esters
listed as adhesion promoting monomers on page 16 of the 1994
Sartomer Product Catalog, including mono-, di- and tri-functional
acrylate or methacrylate ester monomers.
[0051] According to embodiments of the invention, the formulation
may comprise a curing agent to promote or enable curing of the
resinous material. The curing agent may be a catalyst, an initiator
or a reactant. According to embodiments of the invention, the
curing agent may be a free-radical initiator, a cationic catalyst,
a photoinitiator, a co-catalyst, or a co-agent. The curing agent
may catalyze or initiate a reaction which results in a hardening of
the resinous material, for example, a polymerization or
cross-linking reaction. The curing agent may be a reaction
promotor, which promotes, as opposed to catalyzes, a hardening
reaction such as a polymerization or cross-linking reaction.
[0052] The amount of curing agent to be used, if any, will depend
upon the hardening mechanism of the resinous material. The curing
agent should be present in an amount sufficient to harden the
resinous material and trap generated gas bubbles therein, yet not
in an amount which substantially adversely affects the hardness of
the cured coating or the porosity of the exposed surface of the
coating.
[0053] According to embodiments of the invention, the resinous
material comprises an epoxy resin and a curing agent. The curing
agent may be used in amounts of from about 1 part by weight to
about 100 parts by weight based on 100 parts by weight epoxy resin.
The curing agent may be a catalyst or a reactant, for example, the
reactant dicyandiamide. For example, in formulations according to
embodiments of the invention wherein a novolac epoxy resin is used
as the resinous material, an exemplary curing agent may comprise
dicyandiamide, preferably in an amount of from about 5 parts by
weight to about 10 parts by weight based on 100 parts by weight of
the novolac epoxy resin, for example, about 8 parts by weight
dicyandiamide.
[0054] According to some embodiments of the invention, a novolac
epoxy resin is used in combination with a dicyandiamide curing
agent. An exemplary high functionality novolac epoxy resin is
D.E.N. 439, available from The Dow Chemical Company, Midland, Mich.
D.E.N. 439 has an epoxy functionality of 3.9, an epoxy equivalent
weight of about 220, and a high cross-link density. Dicyandiamide
may be included in the coating formulation in an amount of from
about 5 parts by weight to about 10 parts by weight, preferably
about 8 parts by weight based on 100 parts by weight of the D.E.N.
epoxy resin.
[0055] Another curing agent which may be used according to
embodiments of the invention wherein the resinous material
comprises an epoxy resin is methyl hexahydro phthalic anhydride
(MHHPA). MHHPA is available from Anhydrides and Chemicals Inc., of
Newark, N.J. MHHPA may preferably be used in an amount of from
about 85 to about 90 parts by weight based on 100 parts by weight
of an epoxy resinous material having an epoxy functionality of from
about 175 to about 210.
[0056] Other epoxy curing agents and epoxy diluents are described
in the Air Products bulletin Epoxy Curing Agents and Diluents
Product Guide (1992) and include the dicyandiamides AMICURE CG-1200
and AMICURE CG-1400, the imidazoles CUREZOL 2MZ-Azine, CUREZOL
2PHZ-S, and CUREZOL 2MA-OK, and the modified aliphatic amines
ANCAMINE 2014AS, and ANCAMINE 2014FG, all available from Air
Products and Chemicals, Inc., Allentown, Pa.
[0057] According to embodiments of the invention, one or more
solvent may be included in the coating formulation. A solvent may
be included to decrease the viscosity of the formulation, for
example, to make the formulation more easily printable for
application to a laboratory apparatus. The selection of a solvent
depends upon the coating formulation, and generally depends upon
the solubility of the resinous material in the solvent. For
example, preferred solvents for a novolac epoxy may be
triethylphosphate (TEP) and ethylene glycol. Other solvents may
include methyl ethyl ketone, acetone, toluene, xylene and other
organic solvents. A preferred epoxy resin solvent is a mixture of
TEP in methyl ethyl ketone in a weight ratio of, for example, about
3:1. For some resins, including water-soluble silicone resins,
water may be a preferred solvent. For a dry-melt resin powder
formulation, the formulation may be substantially free of
solvent.
[0058] The amount of solvent to be included generally will depend
on the particular resinous material employed and the desired
viscosity of the coating formulation. According to embodiments of
the invention, the amount of solvent present in the coating
formulation may be from 0 to about 500 parts by weight based on 100
parts by weight of the resinous material, for example, from 0 to
about 200 parts by weight solvent.
[0059] According to embodiments of the invention, from about 1 part
by weight to about 100 parts by weight epoxy solvent, based on 100
parts by weight of the resinous material, may be included in
coating formulations containing an epoxy resinous materials. Epoxy
solvents can be added to liquefy the epoxy monomer or resin or
adjust the viscosity thereof. A separate epoxy solvent may not be
needed according to some embodiments of the invention wherein the
epoxy is liquid at room temperature or wherein a fluorinated
monomer or surfactant component of the coating formulation acts as
a solvent for the epoxy.
[0060] According to embodiments of the invention, the formulation
may comprise a dispersing agent. If present, a dispersing agent may
be used in an amount of up to about 50 parts by weight based on 100
parts by weight resinous material. According to embodiments of the
invention, up to about 20 parts by weight dispersing agent may be
included in the coating formulation, based on 100 parts by weight
resinous material, for example, up to about 5 parts by weight
dispersing agent. The dispersing agent may comprise a
fluoroadditive micropowder.
[0061] A preferred dispersing agent is the micropowder
fluoroadditive Teflon.RTM. MP 1200, available from DuPont Polymer
Products Department, Wilmington, Del., and described in the DuPont
Technical Information bulletin Teflon.RTM. MP 1200 (1994).
Teflon.RTM. MP 1200 has an average particle diameter of about 4
.mu.m. Teflon.RTM. MP 1200, and other dispersing agents, aid in
substantially homogeneously dispersing the blowing agent throughout
the resinous material. Dispersing agents preferably provide a
uniform distribution of gas cells throughout at least the surface
of a hardened coating made from the formulations of the
invention.
[0062] According to embodiments of the invention, the coating
formulation may include one or more pigment. The amount of a
pigment which may be used will depend upon the color strength of
the particular pigment and the desired shade of the pigment.
According to some embodiments of the invention, from 0 to about 300
parts by weight pigment may be used in the coating formulation,
based upon 100 parts by weight resinous material.
[0063] Pigments which may be used in accordance with the invention
include ferrous oxides, titanium dioxides, cobalt titanate green
spinels, nickel antimony titanium yellow rutiles, and cobalt
chromite blue-green spinels. Commercially available pigments which
may be used include the pigments Ferro RED, GREEN 50 (green pigment
product code V-11633), YELLOW 53 (yellow pigment product code
V-9412), GREEN 50 (blue pigment product code V-9229) and BLUE 36
(blue pigment product code V-9238), all available from Ferro
Corporation, Edison, N.J.; RED LAKE C available from Sun Chemical
Corporation, Cincinnati, Ohio; and TI-PURE (titanium dioxide white
pigment) available from Du Pont Company, Wilmington, Del.
[0064] According to embodiments of the invention, a kit is provided
which has a base resin mixture and a selection of pigments which
may be added to portions of the base mixture to form any of a wide
variety of colored porous coating formulations. Mixtures of
pigments may be added to a portion of the base mixture to provide
colors other than primary colors, for example, orange, purple and
pink.
[0065] In addition to the foregoing additives, other agents
including flow control agents, leveling agents, surfactants and
plasticizers, including high molecular weight polymers,
fluorosurfactants, and silicone surfactants, may be included in the
coating formulations according to embodiments of the present
invention. Coating formulations according to embodiments of the
invention may comprise such agents to improve printability and
applicability of the formulation, and/or to improve the texture,
appearance and uniformity of a hardened coating made from the
formulation.
[0066] According to embodiments of the invention, the surface
energy or surface chemistry of the porous surface may be adjusted
using selected resins, co-resins or surface-active agents to best
accommodate marking materials or to best facilitate cell growth.
Agents which may be used according to embodiments of the invention,
to adjust surface energy, include surfactants, fluorosurfactants
and siliconized glass particles. Resins and co-resins having polar,
nonpolar, charged, uncharged, aromatic, saturated or sequenced
substituents or backbones may be used to adjust surface
chemistry.
[0067] Porous-coated laboratory apparatus according to embodiments
of the present invention may comprise a wide variety of materials.
Plastic or glass is often used to manufacture low-cost laboratory
apparatus. Some preferred materials used to manufacture laboratory
apparatus include silica glass, polypropylene, polyethylene,
polyethyleneterephthalate, polystyrene, polycarbonate and
cellulosics. Glass products including silica glass are commonly
used to manufacture laboratory vessels. One exemplary glass product
is PYREX.RTM. (available from Coming Glass, Coming, N.Y.).
Laboratory apparatus comprising relatively expensive plastics such
as polytetrafluoroethylene and other fluorinated polymers may also
be used. Because polypropylene is inexpensive, it is a particularly
preferred material for laboratory vessels, including pipette tips,
used for handling and transporting minute and precise amounts of
biological sample.
[0068] In addition to the materials mentioned above, examples of
other suitable materials for the laboratory apparatus of the
present invention include polyolefins, polyamides, polyesters,
silicones, polyurethanes, epoxies, acrylics, polyacrylates,
polyesters, polysulfones, polymethacrylates, polycarbonate, PEEK,
polyimide, polystyrene, and fluoropolymers such as PTFE
Teflon.RTM., FEP Teflon.RTM., Tefzel.RTM., poly(vinylidene
fluoride), PVDF, and perfluoroalkoxy resins. Ceramic or oxide
surfaces may be coated according to embodiments of the invention.
Cellulosic products, for example, paper and reinforced paper
containers, can be coated to form coated laboratory apparatus
according to embodiments of the invention. Metal surfaces can be
coated according to the invention, as can surfaces of glass,
silicon, silicon compounds or ceramics that may or may not have
been primed with silane containing materials or other adhesion
promoting materials. Primed metal, primed glass, primed ceramic and
primed oxide surfaces may be coated with coating formulations
according to embodiments of the invention. Apparatus surfaces that
have been pre-coated with epoxies, silicones, urethanes, acrylics,
or other materials can also be coated according to embodiments of
the invention.
[0069] Preferred methods for applying the coating formulations of
the present invention are pad printing methods. Other coating
methods may be used, including screen printing, spray coating,
brush coating, fogging, transferring, painting, stenciling and ink
jet printing.
[0070] After forming a first coating of polymer according to the
invention, the methods of the invention may also comprise applying
at least one other coating formulation to the first coating.
EXAMPLE 1
[0071] A highly chemically and solvent resistant porous coating for
a microscope slide was prepared. The coating was provided from a
coating formulation having the following ingredients:
[0072] 850 grams high functionality novolac epoxy resin, available
as D.E.N. 439 from The Dow Chemical Company, Midland, Mich., having
an epoxy functionality of 3.9, an epoxy equivalent weight of about
220, and a high cross-link density;
[0073] 70 grams dicyandiamide as a reactant agent for curing the
epoxy, based on the weight of the epoxy;
[0074] 43 grams gamma-glycidoxypropyltrimethoxysilane adhesion
promoter;
[0075] 2125 grams calcinated pigment;
[0076] 450 grams epoxy solvent triethylphosphate to liquefy and
reduce the viscosity of the epoxy;
[0077] 8 grams TEFLON MP 1200 dispersing agent; and
[0078] 8 grams FLUORINERT Liquid FC-70 blowing agent.
[0079] The coating formulation was mixed, screen printed on a
microscope slide and heat cured at 180.degree. C. for 30 minutes.
The resultant cured and dried coating exhibited excellent chemical
resistance to sodium hydroxide solution and to boiling water. The
porous surface of the coating exhibited excellent and permanent
retention of pen and pencil marking materials. The porous surface
was very hard and had a pencil hardness of greater than 8 using
penetration of a 1 mil-thick coating using 1 pound of normal force
for hardness testing.
EXAMPLE 2 AND COMPARATIVE 1
[0080] The chemical resistance and hardness of a coating (Example
2) made from the coating formulation of Example 1 above was
compared to the chemical resistance and hardness of a
SUPERFROST.TM. coating (Comparative 1) available from Erie
Scientific Corporation, Portsmouth, N.H. The SUPERFROST.TM. coating
is believed to be made in accordance with the teachings of U.S.
Pat. No. 4,481,246 to Melisz et al., discussed above, and is
believed to comprise about 3 times as much, by weight, granular
medium as epoxy resin. Microscope slides coated with the exemplary
formulation of the present invention (Example 2) and the
SUPERFROST.TM. coating formulation (Comparative 1) were soaked for
24 hours in the various liquids and solvents shown in Table I
below. The Table shows the pencil hardness measured to penetrate a
1 mil thick coating of each respective formulation using a 1 pound
normal testing force.
1 TABLE I Pencil Hardness to Penetrate 1 Mil Thick Coating Using 1
Pound of Normal Force SOLVENT USED SUPERFROST FOR COATING PRESENT
INVENTION 24-HOUR SOAK (Comparative 1) (Example 2) no soak 8 >8
acetone 8 >8 ethanol 6 >8 xylene 6 >8 boiling 5 >8
deionized water 2% (w/w) HCl 4 >8 in ethanol 2% (w/w) NaOH 0
>8 in deionized water
[0081] As can be seen from Table I above, the coating formulation
of the present invention exhibits superior chemical resistance and
hardness compared to the SUPERFROST.TM. coating formulation. In
addition, a powder resulted when the SUPERFROST.TM. coating was
abraded with a #8 pencil, whereas no powder resulted from similarly
abrading the Example 2 coating of the present invention. Also, the
SUPERFROST.TM. coating came off spontaneously during soaking in the
2% sodium hydroxide solution whereas the coating of the present
invention was chemically resistant to the sodium hydroxide
solution.
[0082] Although the present invention has been described in
connection with preferred embodiments, it will be appreciated by
those skilled in the art that additions, modifications,
substitutions and deletions not specifically described may be made
without departing from the spirit and scope of the invention
defined in the appended claims.
* * * * *