U.S. patent application number 13/282514 was filed with the patent office on 2012-05-03 for polyamide composite structures and processes for their preparation.
This patent application is currently assigned to E. I. DU PONT DE NEMOURS AND COMPANY. Invention is credited to Andri E. Elia, Olaf Norbert Kirchner, Martyn Douglas Wakeman, Shengmei Yuan.
Application Number | 20120108131 13/282514 |
Document ID | / |
Family ID | 44936546 |
Filed Date | 2012-05-03 |
United States Patent
Application |
20120108131 |
Kind Code |
A1 |
Elia; Andri E. ; et
al. |
May 3, 2012 |
POLYAMIDE COMPOSITE STRUCTURES AND PROCESSES FOR THEIR
PREPARATION
Abstract
Disclosed herein are polyamide composite structures and
processes for their preparation. The disclosed composite structures
comprise a surface, having at least a portion made of a surface
resin composition, and comprise a fibrous material being
impregnated with a matrix resin composition. The surface resin
composition is selected from polyamide compositions comprising a
blend of (A) fully aliphatic polyamides having a melting point of
less than 230.degree. C., and (B) fully aliphatic polyamides having
a melting point of at least 250.degree. C., and wherein the matrix
resin composition is independently selected from (B) or blends of
(A) and (B).
Inventors: |
Elia; Andri E.; (Chadds
Fort, PA) ; Kirchner; Olaf Norbert; (Genolier,
CH) ; Wakeman; Martyn Douglas; (Gland, CH) ;
Yuan; Shengmei; (Newark, DE) |
Assignee: |
E. I. DU PONT DE NEMOURS AND
COMPANY
Wilmington
DE
|
Family ID: |
44936546 |
Appl. No.: |
13/282514 |
Filed: |
October 27, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61408166 |
Oct 29, 2010 |
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61410093 |
Nov 4, 2010 |
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61410100 |
Nov 4, 2010 |
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61410104 |
Nov 4, 2010 |
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61410108 |
Nov 4, 2010 |
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Current U.S.
Class: |
442/147 ;
427/411; 427/412; 428/435; 428/474.4; 442/152; 442/164; 442/179;
442/180; 442/59 |
Current CPC
Class: |
B32B 5/024 20130101;
Y10T 442/20 20150401; B32B 5/26 20130101; Y10T 442/2631 20150401;
C08L 77/06 20130101; C08L 77/06 20130101; C08J 5/043 20130101; B32B
2264/12 20130101; Y10T 442/2041 20150401; B29K 2677/00 20130101;
B32B 2260/023 20130101; Y10T 428/249924 20150401; Y10T 428/24994
20150401; Y10T 428/31623 20150401; B29C 45/14786 20130101; B32B
2307/306 20130101; C08K 7/20 20130101; B32B 2264/10 20130101; C08L
77/06 20130101; B32B 2605/00 20130101; B32B 2260/021 20130101; Y10T
428/31725 20150401; B32B 2260/046 20130101; Y10T 428/249921
20150401; Y10T 442/2762 20150401; B32B 27/12 20130101; B32B
2307/546 20130101; C08K 7/20 20130101; C08L 77/06 20130101; C08L
77/06 20130101; B29K 2709/08 20130101; Y10T 428/31728 20150401;
B29K 2077/00 20130101; B32B 2307/308 20130101; Y10T 442/674
20150401; C08J 2377/06 20130101; B29C 45/0001 20130101; B32B
2262/101 20130101; Y10T 442/2984 20150401; B32B 27/34 20130101;
C08L 2205/02 20130101; Y10T 442/2721 20150401; Y10T 442/2861
20150401; Y10T 442/2992 20150401 |
Class at
Publication: |
442/147 ;
428/435; 428/474.4; 442/59; 442/180; 442/179; 442/164; 442/152;
427/411; 427/412 |
International
Class: |
B32B 27/04 20060101
B32B027/04; B32B 5/02 20060101 B32B005/02; B05D 1/36 20060101
B05D001/36; B32B 17/02 20060101 B32B017/02 |
Claims
1. A composite structure having a surface, which surface has at
least a portion made of a surface resin composition, and comprising
a fibrous material selected from the group consisting of non-woven
structures, textiles, fibrous battings and combinations thereof,
said fibrous material being impregnated with a matrix resin
composition, wherein the surface resin composition is selected from
polyamide compositions comprising a blend of (A) one or more fully
aliphatic polyamides selected from group (I) polyamides having a
melting point of less than 230.degree. C., and (B) one or more
fully aliphatic polyamides selected from group (II) polyamides
having a melting point of at least 250.degree. C., and wherein the
matrix resin composition is independently selected from (B) or
independently selected from blends of (A) and (B).
2. The composite structure according to claim 1, wherein the
fibrous material is made of glass fibers, carbon fibers, aramid
fibers, natural fibers or mixtures thereof.
3. The composite structure according to claim 2, wherein the
fibrous material is made of glass fibers.
4. The composite structure according to claim 1 wherein the fibrous
material is from 30 volume percent to 60 volume percent of the
composite structure.
5. The composite structure according to claim 1 further comprising
one or more additives selected from the group consisting of heat
stabilizers, oxidative stabilizers, reinforcing agents and flame
retardants or combination thereof.
6. The composite structure according claim 1 wherein the one or
more fully aliphatic polyamides selected from group (I) polyamides
is selected form the group consisting of PA 6, PA510, PA512,
PA6/66, PA6/610, PA6/612, PA613, PA615, PA6/66/610, PA6/66/612,
PA6/66/610/612, PA D6/66, PA1010, PA1012, PA11, PA12, PA612,
PA1212.
7. The composite structure according to claim 1 wherein the one or
more fully aliphatic polyamides selected from group (II) polyamides
is selected form the group consisting of PA 66, PA6/66, PA6/66/610,
PA6/66/612, PA6/66/610/612, PA D6/66, PA46.
8. The composite structure according to claim 1 wherein the weight
ratio of the one or more polyamides selected from group (I)
polyamides (A) and the one or more polyamides selected from group
(II) polyamides (B) (A:B) of the matrix polyamide composition and
of the surface polyamide composition is between from about 1:99 to
about 95:5.
9. The composite structure according claim 1 wherein the weight
ratio of the one or more polyamides selected from group (I)
polyamides (A) and the one or more polyamides selected from group
(II) polyamides (B) (A:B) of the matrix polyamide composition is
from about 20:80 to about 30:70.
10. The composite structure according claim 1 wherein the weight
ratio of the one or more polyamides selected from group (I)
polyamides (A) and the one or more polyamides selected from group
(II) polyamides (B) (A:B) of the surface polyamide composition is
from about 20:80 to about 60:40.
11. The composite structure according to claim 1 wherein group (I)
polyamides (A) comprises PA6, PA6/12, PA10/10 solely or in
combinations thereof.
12. The composite structure according to claim 1 wherein group (II)
polyamides (B) comprises PA66, PA46, solely or in combinations
thereof.
13. The composite structure according to claim 1 in the form of a
component for automobiles, trucks, commercial airplanes, aerospace,
rail, household appliances, computer hardware, hand held devices,
recreation and sports, structural component for machines,
structural components for buildings, structural components for
photovoltaic equipments or structural components for mechanical
devices.
14. A process for making the composite structure of claim 1 having
a surface, said process comprises a step of: i) impregnating with a
matrix resin composition a fibrous material selected from non-woven
structures, textiles, fibrous battings and combinations thereof,
said fibrous material being impregnated with a matrix resin
composition, wherein at least a portion of the surface of the
composite structure is made of a surface resin composition, and
wherein the surface resin composition is selected from polyamide
compositions comprising a blend of (A) one or more fully aliphatic
polyamides selected from group (I) fully aliphatic polyamides
having a melting point of less than 230.degree. C.; and (B) one or
more fully aliphatic polyamides selected from group (II) polyamides
having a melting point of at least 250.degree. C., and wherein the
matirx resin composition is indepedently selected from (B) or
independently selected from blends of (A) and (B).
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of U.S.
Provisional Application No. 61/408,166, filed Oct. 29, 2010, which
is now pending, the entire disclosure of which is incorporated
herein by reference; and U.S. Provisional Application Nos.
61/410,093, filed Nov. 4, 2010; 61/410,100, filed Nov. 4, 2010;
61/410,104, filed Nov. 4, 2010; and 61/410,108, filed Nov. 4, 2010,
all of which are now pending, the entire disclosures of which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of composite
structures and processes for their preparation, particularly it
relates to the field of polyamide composite structures.
BACKGROUND OF THE INVENTION
[0003] With the aim of replacing metal parts for weight saving and
cost reduction while having comparable or superior mechanical
performance, structures based on composite materials comprising a
polymer matrix containing a fibrous material have been developed.
With this growing interest, fiber reinforced plastic composite
structures have been designed because of their excellent physical
properties resulting from the combination of the fibrous material
and the polymer matrix and are used in various end-use
applications. Manufacturing techniques have been developed for
improving the impregnation of the fibrous material with a polymer
matrix to optimize the properties of the composite structure.
[0004] In highly demanding applications, such as for example
structural parts in automotive and aerospace applications,
composite materials are desired due to a unique combination of
lightweight, high strength and temperature resistance.
[0005] High performance composite structures can be obtained using
thermosetting resins or thermoplastic resins as the polymer matrix.
Thermoplastic-based composite structures present several advantages
over thermoset-based composite structures such as, for example, the
fact that they can be post-formed or reprocessed by the application
of heat and pressure, that a reduced time is needed to make the
composite structures because no curing step is required, and their
increased potential for recycling. Indeed, the time consuming
chemical reaction of cross-linking for thermosetting resins
(curing) is not required during the processing of thermoplastics.
Among thermoplastic resins, polyamides are particularly well suited
for manufacturing composite structures. Thermoplastic polyamide
compositions are desirable for use in a wide range of applications
including parts used in automobiles, electrical/electronic parts,
household appliances and furniture because of their good mechanical
properties, heat resistance, impact resistance and chemical
resistance and because they may be conveniently and flexibly molded
into a variety of articles of varying degrees of complexity and
intricacy.
[0006] U.S. Pat. No. 4,255,219 discloses a thermoplastic sheet
material useful in forming composites. The disclosed thermoplastic
sheet material is made of polyamide 6 and a dibasic carboxylic acid
or anhydride or esters thereof and at least one reinforcing mat of
long glass fibers encased within said layer.
[0007] For making integrated composite structures and to increase
the performance of polymers, it is often desired to "overmold" one
or more parts made of a polymer onto a portion or all of the
surfaces of a composite structure so as to surround or encapsulate
said surfaces. Overmolding involves shaping, e.g. by injection
molding, a second polymer part directly onto at least a portion of
one or more surfaces of the composite structure, to form a two-part
composite structure, wherein the two parts are adhered one to the
other at least at one interface. The polymer compositions used to
impregnate the fibrous material (i.e. the matrix polymer
composition) and the polymer compositions used to overmold the
impregnated fibrous material (i.e. the overmolding polymer
composition) are desired to have good adhesion one to the other,
extremely good dimensional stability and retain their mechanical
properties under adverse conditions, including thermal cycling, so
that the composite structure is protected under operating
conditions and thus has an increased lifetime.
[0008] Unfortunately, conventional thermoplastic polyamide resin
compositions that are used to impregnate one or more fibrous layers
and to overmold the one or more impregnated fibrous layers may
require excessive heating during stamping, forming, or shaping,
which may render their surfaces poor in appearance and in
functionality, and/or may show poor adhesion between the overmolded
polymer and the surface of the component comprising the fibrous
material, i.e. the composite structure. The poor adhesion may
result in the formation of cracks at the interface of the
overmolded composite structures leading to reduced mechanical
properties, premature aging and problems related to delamination
and deterioration of the article upon use and time.
[0009] In such case of weak adhesion, the interface between the
composite structure and the overmolding resin will break first,
rendering the overmolded composite structure weaker than either of
its components. Therefore, high adhesion strength between the
components is highly desirable. However, once the bonding strength
is high enough that the interface can sustain the applied load
without being the first to break, yet higher mechanical performance
of the structure is highly desirable as is needed for the most
highly demanding applications. Lower mechanical performance in
these most demanding applications may impair the durability and
safety of the article upon use and time. Flexural strength, i.e.
the maximum flexural stress sustained by the test specimen during a
bending test, is commonly used as an indication of a material's
ability to bear (or to sustain, or to support) load when flexed.
When overmolding a resin composition onto at least a portion of a
composite structure, high mechanical performance such as flexural
strength of the structure is desired beyond that realized by good
bonding strength between the composite structure and the
overmolding resin.
[0010] There is a need for a thermoplastic polyamide composite
structure that is easier to process in forming, shaping, or
stamping, that exhibits good mechanical properties, especially
flexural strength and having at least a portion of its surface
allowing a good adhesion between its surface and an overmolding
resin comprising a polyamide resin.
SUMMARY OF THE INVENTION
[0011] Described herein is a composite structure having a surface,
which surface has at least a portion made of a surface resin
composition, and comprising a fibrous material selected from
non-woven structures, textiles, fibrous battings and combinations
thereof, said fibrous material being impregnated with a matrix
resin composition, wherein the surface resin composition is
selected from polyamide compositions comprising a blend of (A) one
or more fully aliphatic polyamides selected from group (I)
polyamides having a melting point of less than 230.degree. C., and
(B) one or more fully aliphatic polyamides selected from group (II)
polyamides having a melting point of at least 250.degree. C., and
wherein the matrix resin composition is independently selected from
(B) or independently selected from blends of (A) and (B).
[0012] Further described herein is a process for making the
composite structure described above. The process for making the
composite structure described above comprises a step of i)
impregnating with the matrix resin composition the fibrous
material, wherein at least a portion of the surface of the
composite structure is made of the surface resin composition.
DETAILED DESCRIPTION
[0013] The composite structure according to the present invention
has improved impact resistance and flexural strength and allows a
good adhesion when a part made of an overmolding resin composition
comprising a thermoplastic polyamide is adhered onto at least a
portion of the surface of the composite structure. A good impact
resistance and flexural strength of the composite structure and a
good adhesion between the composite structure and the overmolding
resin leads to structures exhibiting good resistance to
deterioration and resistance to delamination of the structure with
use and time.
[0014] Several patents and publications are cited in this
description. The entire disclosure of each of these patents and
publications is incorporated herein by reference.
[0015] As used herein, the term "a" refers to one as well as to at
least one and is not an article that necessarily limits its
referent noun to the singular.
[0016] As used herein, the terms "about" and "at or about" are
intended to mean that the amount or value in question may be the
value designated or some other value about the same. The phrase is
intended to convey that similar values promote equivalent results
or effects according to the invention.
[0017] As used herein, the term "melting point" in reference to a
polyamide refers to the melting point of the pure resin as
determined with differential scanning calorimetry (DSC) at a scan
rate of 10.degree. C./min in the first heating scan, wherein the
melting point is taken at the maximum of the endothermic peak. In
customary measurements of melting behavior of blends of polymers,
more than one heating scans may be performed on a single specimen,
and the second and/or later scans may show a different melting
behavior from the first scan. This different melting behavior may
be observed as a shift in temperature of the maximum of the
endothermic peak and/or as a broadening of the melting peak with
possibly more than one peaks, which may be an effect of possible
transamidation in the case of more than one polyamides. However,
when selecting polyamides for Group I or for Group II polyamides in
the scope of the current invention, always the peak of the melting
endotherm of the first heating scan of the single polyamide is
used. As used herein, a scan rate is an increase of temperature per
unit time. Sufficient energy must be supplied to maintain a
constant scan rate of 10.degree. C./min until a temperature of at
least 30.degree. C. and preferably at least 50.degree. C. above the
melting point is reached.
[0018] The present invention comprises a fibrous material that is
impregnated with a matrix resin composition. At least a portion of
the surface of the composite structure is made of a surface resin
composition. The matrix resin composition and the surface resin
composition may be identical or may be different.
[0019] As used herein, the term "a fibrous material being
impregnated with a matrix resin composition" means that the matrix
resin composition encapsulates and embeds the fibrous material so
as to form an interpenetrating network of fibrous material
substantially surrounded by the matrix resin composition. For
purposes herein, the term "fiber" refers to a macroscopically
homogeneous body having a high ratio of length to width across its
cross-sectional area perpendicular to its length. The fiber cross
section can be any shape, but is typically round. The fibrous
material may be in any suitable form known to those skilled in the
art and is preferably selected from non-woven structures, textiles,
fibrous battings and combinations thereof. Non-woven structures can
be selected from random fiber orientation and aligned fibrous
structures. Examples of random fiber orientation include without
limitation chopped and continuous material which can be in the form
of a mat, a needled mat or a felt. Examples of aligned fibrous
structures include without limitation unidirectional fiber strands,
bidirectional strands, multidirectional strands, multi-axial
textiles. Textiles can be selected from woven forms, knits, braids
and combinations thereof. The fibrous material can be continuous or
discontinuous in form.
[0020] Depending on the end-use application of the composite
structure and the required mechanical properties, more than one
fibrous materials can be used, either by using several same fibrous
materials or a combination of different fibrous materials, i.e. the
first component described herein may comprise one or more fibrous
materials. An example of a combination of different fibrous
materials is a combination comprising a non-woven structure such as
for example a planar random mat which is placed as a central layer
and one or more woven continuous fibrous materials that are placed
as outside layers. Such a combination allows an improvement of the
processing and thereof of the homogeneity of the first component
thus leading to improved mechanical properties. The fibrous
material may be made of any suitable material or a mixture of
materials provided that the material or the mixture of materials
withstand the processing conditions used during impregnation by the
matrix resin composition and the surface resin composition.
[0021] Preferably, the fibrous material comprises glass fibers,
carbon fibers, aramid fibers, graphite fibers, metal fibers,
ceramic fibers, natural fibers or mixtures thereof; more
preferably, the fibrous material comprises glass fibers, carbon
fibers, aramid fibers, natural fibers or mixtures thereof; and
still more preferably, the fibrous material comprises glass fibers,
carbon fibers and aramid fibers or mixture mixtures thereof. By
natural fiber, it is meant any of material of plant origin or of
animal origin. When used, the natural fibers are preferably derived
from vegetable sources such as for example from seed hair (e.g.
cotton), stem plants (e.g. hemp, flax, bamboo; both bast and core
fibers), leaf plants (e.g. sisal and abaca), agricultural fibers
(e.g., cereal straw, corn cobs, rice hulls and coconut hair) or
lignocellulosic fiber (e.g. wood, wood fibers, wood flour, paper
and wood-related materials). As mentioned above, more than one
fibrous materials can be used. A combination of fibrous materials
made of different fibers can be used such as for example a
composite structure comprising one or more central layers made of
glass fibers or natural fibers and one or more surface layers made
of carbon fibers or glass fibers. Preferably, the fibrous material
is selected from woven structures, non-woven structures and
combinations thereof, wherein said structures are made of glass
fibers and wherein the glass fibers are E-glass filaments with a
diameter between 8 and 30 microns and preferably with a diameter
between 10 to 24 microns.
[0022] The fibrous material may further contain a thermoplastic
material and the materials described above, for example the fibrous
material may be in the form of commingled or co-woven yarns or a
fibrous material impregnated with a powder made of a thermoplastic
material that is suited to subsequent processing into woven or
non-woven forms, or a mixture for use as a uni-directional material
or a fibrous material impregnated with oligomers that will
polymerize in situ during impregnation.
[0023] Preferably, the ratio between the fibrous material and the
polymer materials in the first component. i.e. the fibrous material
in combination with the matrix resin composition and the surface
resin composition, is at least 30 volume percent fibrous material
and more preferably between 40 and 60 volume percent fibrous
material, the percentage being a volume-percentage based on the
total volume of the first component.
[0024] The matrix resin composition is made of a thermoplastic
resin that is compatible with the surface resin composition. The
surface resin composition is selected from polyamide compositions
comprising a blend of (A) one or more fully aliphatic group (I)
polyamides having a melting point of less than 230.degree. C. and
(B) one or more fully aliphatic polyamides selected from group (II)
polyamides having a melting point of at least 250.degree. C. The
matrix resin composition is independently selected from (B) or
independently selected from blends of (A) and (B). The matrix resin
composition and the surface resin composition may be identical or
different. When the surface resin composition and the matrix resin
composition are different, and when the matrix resin composition is
selected from blends of (A) and (B), it means that the component
(A), i.e. the one or more group (I) fully aliphatic polyamides
having a melting point of less than 230.degree. C., and/or the
component (B), i.e. the one or more fully aliphatic polyamides
selected from group (II) polyamides having a melting point of at
least 250.degree. C., are not the same and/or that the amounts of
component (A) and/or (B) are different in the surface resin
composition and the matrix resin composition.
[0025] Preferably, the matrix resin composition comprises a blend
of (A) the one or more group (I) polyamides and (B) one or more
polyamides selected from group (II) polyamides in a weight ratio
(A:B) from about 1:99 to about 95:5, more preferably from about
15:85 to about 85:15. Still more preferably the matrix resin
composition comprises a blend of (A) the one or more group (I)
polyamides and (B) one or more polyamides selected from group (II)
polyamides in a weight ratio (A:B) from about 20:80 to about 30:70,
or is selected solely from one or more polyamides B.
[0026] Preferably, the surface resin composition comprises a blend
of (A) the one or more group (I) polyamides and (B) one or more
polyamides selected from group (II) polyamides (B) in a weight
ratio (A:B) from about 1:99 to about 95:5, more preferably from
about 15:85 to about 85:15, and still more preferably 40:60 to
about 60:40.
[0027] Polyamides are condensation products of one or more
dicarboxylic acids and one or more diamines, and/or one or more
aminocarboxylic acids, and/or ring-opening polymerization products
of one or more cyclic lactams.
[0028] The one or more fully aliphatic polyamides (A) and (B) are
formed from aliphatic and alicyclic monomers such as diamines,
dicarboxylic acids, lactams, aminocarboxylic acids, and their
reactive equivalents. A suitable aminocarboxylic acid is
11-aminododecanoic acid. Suitable lactams include caprolactam and
laurolactam. In the context of this invention, the term "fully
aliphatic polyamide" also refers to copolymers derived from two or
more such monomers and blends of two or more fully aliphatic
polyamides. Linear, branched, and cyclic monomers may be used.
Carboxylic acid monomers comprised in the fully aliphatic
polyamides are aliphatic carboxylic acids, such as for example
adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic
acid (C9), sebacic acid (C10), dodecanedioic acid (C12) and
tetradecanedioic acid (C14). Preferably, the aliphatic dicarboxylic
acids of the one or more fully aliphatic polyamides (A) and (B) are
selected from adipic acid and dodecanedioic acid. The one or more
fully aliphatic polyamides (A) and (B) described herein comprise an
aliphatic diamine as previously described. Preferably, the one or
more diamine monomers of the one or more fully aliphatic polyamide
copolymer (A) and (B) according to the present invention are
selected from tetramethylene diamine and hexamethylene diamine.
Suitable examples fully aliphatic polyamides include polyamide 6;
polyamide 6,6; polyamide 4,6; polyamide 6,10; polyamide 6,12;
polyamide 6,14; polyamide 6,13; polyamide 6,15; polyamide 6,16;
polyamide 11; polyamide 12; polyamide 9,10; polyamide 9,12;
polyamide 9,13; polyamide 9,14; polyamide 9,15; polyamide 6,16;
polyamide 9,36; polyamide 10,10; polyamide 10,12; polyamide 10,13;
polyamide 10,14; polyamide 12,10; polyamide 12,12; polyamide 12,13;
polyamide 12,14. Preferred examples of fully aliphatic polyamides
(B) useful in the polyamide composition of the present invention
are poly(hexamethylene adipamide) (polyamide 66, PA66, also called
nylon 66), and poly(tetramethylene adipamide) (polyamide 46, PA46,
also called nylon 46).
[0029] Preferred group (I) polyamides having a melting point of
less than 230.degree. C. comprise a fully aliphatic polyamide
selected from the group consisting of poly(.epsilon.-caprolactam)
(PA 6), and poly(pentamethylene decanediamide) (PA510),
poly(pentamethylene dodecanediamide) (PA512),
poly(.epsilon.-caprolactam/hexamethylene hexanediamide) (PA6/66),
poly(.epsilon.-caprolactam/hexamethylene decanediamide) (PA6/610),
poly(.epsilon.-caprolactam/hexamethylene dodecanediamide)
(PA6/612), poly(hexamethylene tridecanediamide) (PA613),
poly(hexamethylene pentadecanediamide) (PA615),
poly(.epsilon.-caprolactam/hexamethylene
hexanediamide/hexamethylene decanediamide) (PA6/66/610),
poly(.epsilon.-caprolactam/hexamethylene
hexanediamide/hexamethylene dodecanediamide) (PA6/66/612),
poly(.epsilon.-caprolactam/hexamethylene
hexanediamide/hexamethylene decanediamide/hexamethylene
dodecanediamide) (PA6/66/610/612), poly(2-methylpentamethylene
hexanediamide/hexamethylene hexanediamide/) (PA D6/66),
poly(decamethylene decanediamide) (PA1010), poly(decamethylene
dodecanediamide) (PA1012), poly(11-aminoundecanamide) (PA11),
poly(12-aminododecanamide) (PA12), PA6,12, PA12,12.
[0030] Preferred group (II) polyamides having a melting point of at
least 250.degree. C., are polyamides selected from the group
poly(hexamethylene hexanediamide) (PA 66),
poly(.epsilon.-caprolactam/hexamethylene hexanediamide) (PA6/66),
(PA6/66/610), poly(.epsilon.-caprolactam/hexamethylene
hexanediamide/hexamethylene dodecanediamide) (PA6/66/612),
poly(.epsilon.-caprolactam/hexamethylene
hexanediamide/hexamethylene decanediamide/hexamethylene
dodecanediamide) (PA6/66/610/612), poly(2-methylpentamethylene
hexanediamide/hexamethylene hexanediamide/) (PA D6/66),
poly(tetramethylene hexanediamide) (PA46).
[0031] An embodiment of the current invention comprises a matrix
resin composition and a surface resin composition comprising PA6
(group (I) polyamide A) and PA66 (group (II) polyamide B) in an A:B
ratio of 25:75.
[0032] A preferred embodiment of the current invention comprise a
matrix resin composition comprising PA6 (group (I) polyamide A) and
PA66 (group (II) polyamide B) in a A:B ratio of 25:75 and a surface
resin composition comprising PA6 (group (I) polyamide A) and PA66
(group (II) polyamide B) in an A:B ratio of 50:50.
[0033] Another preferred embodiment of the current invention
comprise a matrix resin composition comprising PA66 (group (II)
polyamide B) and a surface resin composition comprising PA6 (group
(I) polyamide A) and PA66 (group (II) polyamide B) in an A:B ratio
of 50:50.
[0034] The surface resin composition described herein and/or the
matrix resin composition may further comprise one or more impact
modifiers, one or more heat stabilizers, one or more oxidative
stabilizers, one or more ultraviolet light stabilizers, one or more
flame retardant agents or mixtures thereof.
[0035] The surface resin composition described herein and/or the
matrix resin composition may further comprise one or more
reinforcing agents such as glass fibers, glass flakes, carbon
fibers, carbon nanotubes, mica, wollastonite, calcium carbonate,
talc, calcined clay, kaolin, magnesium sulfate, magnesium silicate,
boron nitride, barium sulfate, titanium dioxide, sodium aluminum
carbonate, barium ferrite, and potassium titanate. When present,
the one or more reinforcing agents are present in an amount from at
or about 1 to at or about 60 wt-%, preferably from at or about 1 to
at or about 40 wt-%, or more preferably from at or about 1 to at or
about 35 wt-%, the weight percentages being based on the total
weight of the surface resin composition or the matrix resin
composition, as the case may be.
[0036] As mentioned above, the matrix resin composition and the
surface resin composition may be identical or different. With the
aim of increasing the impregnation rate of the fibrous material,
the melt viscosity of the compositions may be reduced and
especially the melt viscosity of the matrix resin composition.
[0037] The surface resin composition described herein and/or the
matrix resin composition may further comprise modifiers and other
ingredients, including, without limitation, flow enhancing
additives, lubricants, antistatic agents, coloring agents
(including dyes, pigments, carbon black, and the like), nucleating
agents, crystallization promoting agents and other processing aids
known in the polymer compounding art.
[0038] Fillers, modifiers and other ingredients described above may
be present in the composition in amounts and in forms well known in
the art, including in the form of so-called nano-materials where at
least one of the dimensions of the particles is in the range of 1
to 1000 nm.
[0039] Preferably, the surface resin compositions and the matrix
resin compositions are melt-mixed blends, wherein all of the
polymeric components are well-dispersed within each other and all
of the non-polymeric ingredients are well-dispersed in and bound by
the polymer matrix, such that the blend forms a unified whole. Any
melt-mixing method may be used to combine the polymeric components
and non-polymeric ingredients of the present invention. For
example, the polymeric components and non-polymeric ingredients may
be added to a melt mixer, such as, for example, a single or
twin-screw extruder; a blender; a single or twin-screw kneader; or
a Banbury mixer, either all at once through a single step addition,
or in a stepwise fashion, and then melt-mixed. When adding the
polymeric components and non-polymeric ingredients in a stepwise
fashion, part of the polymeric components and/or non-polymeric
ingredients are first added and melt-mixed with the remaining
polymeric components and non-polymeric ingredients being
subsequently added and further melt-mixed until a well-mixed
composition is obtained.
[0040] Depending on the end-use application, the composite
structure according to the present invention may have any shape. In
a preferred embodiment, the composite structure according to the
present invention is in the form of a sheet structure. The
composite structure may be flexible, in which case it can be
rolled.
[0041] The composite structure can be made by a process that
comprises a step of impregnating the fibrous material with the
matrix resin composition, wherein at least a portion of the surface
of the composite structure, is made of the surface resin
composition. Preferably, the fibrous material is impregnated with
the matrix resin by thermopressing. During thermopressing, the
fibrous material, the matrix resin composition and the surface
resin composition undergo heat and pressure in order to allow the
resin compositions to melt and penetrate through the fibrous
material and, therefore, to impregnate said fibrous material.
[0042] Typically, thermopressing is made at a pressure between 2
and 100 bars and more preferably between 10 and 40 bars and a
temperature which is above the melting point of the matrix resin
composition and the surface resin composition, preferably at least
about 20.degree. C. above the melting point to enable a proper
impregnation. Heating may be done by a variety of means, including
contact heating, radiant gas heating, infra red heating, convection
or forced convection air heating, induction heating, microwave
heating or combinations thereof.
[0043] The impregnation pressure can be applied by a static process
or by a continuous process (also known as dynamic process), a
continuous process being preferred for reasons of speed. Examples
of impregnation processes include without limitation vacuum
molding, in-mold coating, cross-die extrusion, pultrusion, wire
coating type processes, lamination, stamping, diaphragm forming or
press-molding, lamination being preferred. During lamination, heat
and pressure are applied to the fibrous material, the matrix resin
composition and the surface resin composition through opposing
pressured rollers or belts in a heating zone, preferably followed
by the continued application of pressure in a cooling zone to
finalize consolidation and cool the impregnated fibrous material by
pressurized means. Examples of lamination techniques include
without limation calendering, flatbed lamination and double-belt
press lamination. When lamination is used as the impregnating
process, preferably a double-belt press is used for lamination.
[0044] Should the matrix resin composition and the surface resin
composition be different, the surface resin composition always
faces the environment of the first component so as to be accessible
when the overmolding resin composition is applied onto the
composite structure.
[0045] The matrix resin composition and the surface resin
composition are applied to the fibrous material by conventional
means such as for example powder coating, film lamination,
extrusion coating or a combination of two or more thereof, provided
that the surface resin composition is applied on at least a portion
of the surface of the composite structure, which surface is exposed
to the environment of the first component.
[0046] During a powder coating process, a polymer powder which has
been obtained by conventional grinding methods is applied to the
fibrous material. The powder may be applied onto the fibrous
material by scattering, sprinkling, spraying, thermal or flame
spraying, or fluidized bed coating methods. Optionally, the powder
coating process may further comprise a step which consists in a
post sintering step of the powder on the fibrous material. The
matrix resin composition and the surface resin composition are
applied to the fibrous material such that at least a portion of the
surface of the first component is made of the surface resin
composition. Subsequently, thermopressing is performed on the
powder coated fibrous material, with an optional preheating of the
powder coated fibrous material outside of the pressurized zone.
[0047] During film lamination, one or more films made of the matrix
resin composition and one or more films made of the surface resin
composition which have been obtained by conventional extrusion
methods known in the art such as for example blow film extrusion,
cast film extrusion and cast sheet extrusion are applied to the
fibrous material, e.g. by layering. Subsequently, thermopressing is
performed on the assembly comprising the one or more films made of
the matrix resin composition and the one or more films made of the
surface resin composition and the one or more fibrous materials. In
the resulting first component, the films melt and penetrate around
the fibrous material as a polymer continuum surrounding the fibrous
material.
[0048] During extrusion coating, pellets and/or granulates made of
the matrix resin composition and pellets and/or granulates made of
the surface resin composition are melted and extruded through one
or more flat dies so as to form one or more melt curtains which are
then applied onto the fibrous material by laying down the one or
more melt curtains. Subsequently, thermopressing is performed on
the assembly comprising the matrix resin composition, the surface
resin composition and the one or more fibrous materials.
[0049] Depending on the end-use application, the composite
structure obtained under step i) may be shaped into a desired
geometry or configuration, or used in sheet form. The process for
making a composite structure according to the present invention may
further comprise a step ii) of shaping the composite structure,
said step arising after the impregnating step i). The step of
shaping the composite structure obtained under step i) may be done
by compression molding, stamping or any technique using heat and/or
pressure. Preferably, pressure is applied by using a hydraulic
molding press. During compression molding or stamping, the
composite structure is preheated to a temperature above the melt
temperature of the surface resin composition and is transferred to
a forming or shaping means such as a molding press containing a
mold having a cavity of the shape of the final desired geometry
whereby it is shaped into a desired configuration and is thereafter
removed from the press or the mold after cooling to a temperature
below the melt temperature of the surface resin composition and
preferably below the melt temperature the matrix resin
composition.
[0050] The composite structure of the invention is particularly
suited to overmolding with a polyamide overmolding resin
composition. Any polyamide resin can be used for the overmolding
resin composition. Particularly good adhesion is obtained when the
overmolding resin composition is selected from polyamide
compositions selected from (B) or independently selected from
polyamide compositions comprising a blend of (A) one or more fully
aliphatic polyamides selected from group (I) polyamides having a
melting point of less than 230.degree. C., and (B) one or more
fully aliphatic polyamides selected from group (II) polyamides
having a melting point of at least 250.degree. C.
[0051] The composite structures according to the present invention
may be used in a wide variety of applications such as for example
as components for automobiles, trucks, commercial airplanes,
aerospace, rail, household appliances, computer hardware, hand held
devices, recreation and sports, structural component for machines,
structural components for buildings, structural components for
photovoltaic equipments or structural components for mechanical
devices.
[0052] Examples of automotive applications include without
limitation seating components and seating frames, engine cover
brackets, engine cradles, suspension arms and cradles, spare tire
wells, chassis reinforcement, floor pans, front-end modules,
steering column frames, instrument panels, door systems, body
panels (such as horizontal body panels and door panels), tailgates,
hardtop frame structures, convertible top frame structures, roofing
structures, engine covers, housings for transmission and power
delivery components, oil pans, airbag housing canisters, automotive
interior impact structures, engine support brackets, cross car
beams, bumper beams, pedestrian safety beams, firewalls, rear
parcel shelves, cross vehicle bulkheads, pressure vessels such as
refrigerant bottles and fire extinguishers and truck compressed air
brake system vessels, hybrid internal combustion/electric or
electric vehicle battery trays, automotive suspension wishbone and
control arms, suspension stabilizer links, leaf springs, vehicle
wheels, recreational vehicle and motorcycle swing arms, fenders,
roofing frames and tank flaps.
[0053] Examples of household appliances include without limitation
washers, dryers, refrigerators, air conditioning and heating.
Examples of recreation and sports include without limitation
inline-skate components, baseball bats, hockey sticks, ski and
snowboard bindings, rucksack backs and frames, and bicycle frames.
Examples of structural components for machines include
electrical/electronic parts such as for example housings for hand
held electronic devices, computers.
EXAMPLES
[0054] The following materials were used for preparing the
composites structures according to the present invention and
comparative examples.
[0055] Materials
[0056] The materials below are comprised in the compositions used
in the Examples and Comparative Examples.
[0057] Polyamide from group II (B)(PA1 in Tables 1 and 2): a group
II polyamide made of adipic acid and 1,6-hexamethylenediamine with
a weight average molecular weight of around 32000 Daltons. PA1 has
a melting point of about 260.degree. C. to about 265.degree. C. and
a glass transition of about 40.degree. C. to about 70.degree. C.
PA1 is called PA6,6 and is commercially available, for example,
from E. I. du Pont de Nemours and Company.
[0058] Polyamide from group I (A) (PA2 in Tables 1 and 2): a group
I polyamide made of .epsilon.-caprolactam having a melting point of
about 220.degree. C. PA2 is called PA6 and is commercially
available, for example, from BASF corporation.
Preparation of Films
[0059] The resin compositions used in the Examples (abbreviated as
"E" in Tables 1 and 2), and Comparative Example (abbreviated as "C"
in Tables 1 and 2) were prepared by melting or melt-blending the
ingredients in a twin-screw extruder at about 280.degree. C. Upon
exiting the extruder through an adaptor and a film die at about
280.degree. C., the compositions were cast onto a casting drum at
about 100.degree. C. into about 102 micron thick film in the case
of the matrix resin compositions of C1, E1, and E2 (Table 1) and
the surface resin composition of C1 (Table 1), about 200 micron
thick films in the case of the surface resin composition of
Examples E1 and E2 (Table 1), and about 250 micron thick films in
the case of both matrix and surface resin compositions of E3 and C2
(Table 2). The thickness of the films was controlled by the rate of
drawing.
Preparation of the Composite Structures E1, E2, and C1 of Table
1
[0060] The composite structures C1 (comparative), E1, and E2 were
prepared by first making a laminate by stacking eight layers having
a thickness of about 102 microns and made of PA1 and three layers
of woven continuous glass fiber textile (E-glass fibers having a
diameter of 17 microns, 0.4% of a silane-based sizing and a nominal
roving tex of 1200 g/km that have been woven into a 2/2 twill
(balanced weave) with an areal weight of 600 g/m.sup.2) in the
following sequence: two layers made of PA1, one layer of woven
continuous glass fiber textile, two layers of PA1, one layer of
woven continuous glass fiber textile, two layers of PA1, one layer
of woven continuous glass fiber textile and two layers of PA1.
[0061] The laminates were prepared using an isobaric double press
machine with counter rotating steel belts, both supplied by Held
GmbH. The different films enterered the machine from unwinders in
the previously defined stacking sequence. The heating zones were
about 2000 mm long and the cooling zones were about 1000 mm long.
Heating and cooling were maintained without release of pressure.
The laminates were prepared with the following conditions: a
lamination rate of 1 m/min, a maximum machine temperature of
360.degree. C. and laminate pressure of 40 bar. The so-obtained
laminates had an overall thickness of about 1.5 mm.
[0062] Films of about 200 micrometers and made of the surface
polyamide resin compositions of E1 and E2 described in Table 1 were
applied to the above described laminate, forming the composite
structure. The films comprising the surface polyamide resin
compositions were made with a 28 mm W&P extruder with an
adaptor and film die and an oil heated casting drum. The extruder
and adaptor and die temperatures were set at 280.degree. C., and
the temperature of the casting drum was set at 100.degree. C. The
composite structures were formed by compression molding the films
by a Dake Press (Grand Haven, Mich.) Model 44-225 (pressure range
0-25K) with an 8 inch platten. A 6.times.6'' specimen of the
laminate was placed in the mold and the film was pressed onto the
laminate's surface at a tempertature of about 300.degree. C. and
with a pressure of about 3 KPsi for about 2 minutes, and with a
pressure of about 6 Kpsi for about 3 additional minutes and
subsequently cooled to room temperature. The composite structures
comprising a surface made of the surface polyamide resin
compositions of E1 or E2 described in Table 1, the matrix resin
compositions PA1 and the fibrous material had an overall thickness
of about 1.5 mm.
Preparation of the Composite Structures E3 and C2 of Table 2
[0063] Preparation of the composite structures E3 and C2 in Table 2
was accomplished by laminating multiple layers of film of
compositions shown in Table 2 and woven continuous glass fiber
textile (prepared from E-glass fibers having a diameter of 17
microns, sized with 0.4% of a silane-based sizing agent and a
nominal roving tex of 1200 g/km that have been woven into a 2/2
twill (balanced weave) with an areal weight of 600 g/m.sup.2) in
the following sequence: two layers of film of surface resin
composition, one layer of woven continuous glass fiber textile, two
layers of film of matrix resin composition, one layer of woven
continuous glass fiber textile, two layers of film of matrix resin
composition, one layer of woven continuous glass fiber textile, and
two layers of film of surface resin composition.
[0064] The composite structures of table 2 were compression molded
by a Dake Press (Grand Haven, Mich.) Model 44-225, Pressure range
0-25K, with an 8 inch platten. A 6.times.6'' specimen of film and
glass textile layers as described above was placed in the mold and
heated to a temperature of about 320.degree. C., held at the
temperature for 2 minutes without pressure, then pressed at the
320.degree. C. temperature with the following pressures: about 6
bar for about 2 minutes, then with about 22 bar for about 2
additional minutes, and then with about 45 bar for about 2
additional minutes; they were subsequently cooled to ambient
temperature. The thusly formed composite structures had a thickness
of about 1.6 mm.
Bond Strength of Composite Structures C1, E1, and E2 of Table 1
[0065] When composite structures C1, E1, and E2 were over-injection
molded with an overmolding resin composition comprising PA1 and 30
weight percent of glass fibers (percentage of the total composition
of the overmolding resin), the bond strengths were respectively 0,
86, and 121 MPa, demonstrating the superior ability of a blend of
polyamide selected from group 1 with polyamide selected from group
II to form strong bond strength to an overmolding resin, when
compared to a polyamide from one single group of polyamides.
[0066] The over-injection molding was accomplished by
over-injection molding 1.7 mm of the overmolding resin composition
onto the composite structures obtained as described above. The
composite structures C1, E1, and E2 comprising a surface made of
the surface resin compositions listed in Table 1, the matrix resin
compositions listed in Table 1 and the fibrous material described
above were cut into 5.times.5'' (about 127 mm.times.127 mm)
specimens and placed into a heating chamber for 3 min at
180.degree. C. Then the composite structures were quickly
transferred with a robot arm into a mold cavity of an Engel
vertical press and were over injection molded with the overmolding
resin composition comprising PA1 and 30 weight percent of glass
fibers (percentage of the total composition of the overmolding
resin) by an Engel molding machine. The transfer time from leaving
the heating chamber to contact with the overmolding resin was 9
sec. The mold was oil heated at 120.degree. C. The injection
machine was set at 280.degree. C.
[0067] The 5.times.5'' specimens of the overmolded composite
structures comprising E1, E2, and C1 prepared as described above,
were cut into 3/4".times.5" test specimens (about 19 mm.times.about
127 mm), and were notched by cutting the overmolded part up to the
interface of the overmolded part and the composite structure. The
notch was made through the width at about the middle (lengthwise)
of the test specimen. The bond strength of the overmolded resin
composition to the composite structure was measured on the notched
test specimens via a 3 point bend method, modified ISO-178. The
apparatus and geometry were according to ISO method 178, bending
the specimen with a 2.0'' (about 51 mm) support width with the
loading edge at the center of the span. The over-molded part of the
specimen was on the tensile side (outer span) resting on the two
side supports (at 2'' (about 51 mm) apart), while indenting with
the single support (the load) on the compression side (inner span)
on the composite structure of the specimen. In this test geometry,
the notch in the specimens was down (tensile side). The notch was
placed 1/4'' off center (1/4'' away from the load). The tests were
conducted at 2 mm/min. The test was run until a separation or
fracture between the two parts of the specimen (delamination) was
seen. The stress at that point was recorded.
[0068] Flexural Strength of Composite Structures E3 and C2 in Table
2
[0069] The composite structures E3 and C2 in Table 2 were cut into
1/2'' (about 12.7 mm) by 2.5'' (about 64 mm) long test specimens
(bars) using a MK-377 Tile Saw with a diamond edged blade and water
as a lubricant. Flexural Strength was tested on the test specimens
via a 3-point bend test. The apparatus and geometry were according
to ISO method 178, bending the specimen with a 2.0'' support width
with the loading edge at the center of the span. The tests were
conducted with 1 KN load at 2 mm/min until fracture. The results
are shown in Table 2, 380 and 332 MPa for composite structures E3
and C2 respectively, demonstrating the superior flexural strength
of a composite structure made of a blend of polyamide selected from
group 1 with polyamide selected from group II, when compared to a
composite structure made of a polyamide from one single group of
polyamides.
TABLE-US-00001 TABLE 1 Composite Composite Composite structure
structure structure C1 E1 E2 Matrix resin 100 wt-% PA1 100 wt-% PA1
100 wt-% PA1 composition Surface resin 100 wt-% PA1 blend of: blend
of: composition 75 wt-% of PA1 and 50 wt-% of PA1 and 25 wt-% of
PA2 50 wt-% of PA2
TABLE-US-00002 TABLE 2 E3 C2 Matrix Resin Composition PA1 50 100
PA2 50 Surface Resin Composition PA1 50 100 PA2 50 ISO-178 3 Point
Flex Flexural Strength at Break (Mpa) 380 332
* * * * *