U.S. patent application number 09/509085 was filed with the patent office on 2002-02-28 for substantially anhydrous blowing agent and process for producing the same.
Invention is credited to MAEKAWA, TSUKASA, SHONO, SADAFUMI, SUMITOMO, SHIGERU, TACHI, YOSHIFUMI, UEDA, NOBUYUKI.
Application Number | 20020025988 09/509085 |
Document ID | / |
Family ID | 27293973 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020025988 |
Kind Code |
A1 |
MAEKAWA, TSUKASA ; et
al. |
February 28, 2002 |
SUBSTANTIALLY ANHYDROUS BLOWING AGENT AND PROCESS FOR PRODUCING THE
SAME
Abstract
It provides a blowing agent which is significantly inhibited
from solidification and is exceedingly useful as a blowing agent
satisfactory in flowability, dispersibility into resins, and the
like, even after the lapse of a prolonged period of time, and a
process for producing the same. The blowing agent of the present
invention is substantially anhydrous blowing agent, and it is
obtained by treating a blowing agent with a surface-treating agent
capable of removing water from the blowing agent, followed by
optionally heating during or after the treatment.
Inventors: |
MAEKAWA, TSUKASA;
(TOKUSHIMA, JP) ; UEDA, NOBUYUKI; (TOKUSHIMA,
JP) ; SHONO, SADAFUMI; (TOKUSHIMA, JP) ;
TACHI, YOSHIFUMI; (TOKUSHIMA, JP) ; SUMITOMO,
SHIGERU; (TOKUSHIMA, JP) |
Correspondence
Address: |
WHITHAM CURTIS & WHITHAM
RESTON INTERNATIONAL CENTER
11800 SUNRISE VALLEY DRIVE SUITE 900
RESTON
VA
20191
US
|
Family ID: |
27293973 |
Appl. No.: |
09/509085 |
Filed: |
March 22, 2000 |
PCT Filed: |
July 10, 1998 |
PCT NO: |
PCT/JP98/03094 |
Current U.S.
Class: |
521/57 |
Current CPC
Class: |
C08J 9/103 20130101;
C08J 9/00 20130101 |
Class at
Publication: |
521/57 |
International
Class: |
C08J 009/22 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 3, 1998 |
JP |
10/50504 |
Mar 3, 1998 |
JP |
10/50571 |
Apr 27, 1998 |
JP |
10/116822 |
Claims
What is claimed is:
1. A substantially anhydrous blowing agent.
2. A substantially anhydrous blowing agent obtained by treating a
blowing agent with a surface-treating agent capable of removing
water from the blowing agent.
3. The substantially anhydrous blowing agent according to claim 2,
wherein the surface-treating agent is at least one selected from
the group consisting of a coupling agent, an organic acid
anhydride, an anhydrous inorganic compound, and a desiccant.
4. The substantially anhydrous blowing agent according to claim 3,
wherein the surface-treating agent is at least one selected from
the group consisting of a silane coupling agent, an aluminum
coupling agent, and a titanate coupling agent.
5. The substantially anhydrous blowing agent according to claim 4,
wherein the surface-treating agent is an aluminum coupling agent,
and the surface of the blowing agent is coated with aluminum
hydroxide.
6. The substantially anhydrous blowing agent according to any one
of claims 1 to 5, wherein the blowing agent is crystalline
azodicarbonamide.
7. A process for producing a substantially anhydrous blowing agent,
which comprises treating a blowing agent with a surface-treating
agent capable of removing water from the blowing agent under
conditions substantially free of a solvent.
8. The process according to claim 7, wherein heating treatment is
carried out during or after the treatment with the surface-treating
agent.
9. The process according to claim 8, wherein the heating treatment
is carried out at a temperature of 30.degree. C. to the
decomposition temperature of the blowing agent.
10. The process according to claim 9, wherein the heating is
carried out at a temperature of 55 to 100.degree. C.
11. The process according to any one of claims 8 to 10, wherein the
surface-treating agent is subjected to preheating treatment.
12. The process according to any one of claims 7 to 11, wherein the
treatment of the blowing agent with the surface-treating agent is
carried out by spraying the surface-treating agent to the blowing
agent, and mixing them under mixing conditions where pulverization
of a blowing agent is inhibited.
13. The process according to claim 12, wherein a ribbon blender or
a screw mixer is used as a mixer under the mixing conditions where
pulverization of a blowing agent is inhibited.
14. The process according to any one of claims 7 to 13, wherein the
blowing agent is crystalline azodicarbonamide.
15. The process according to any one of claims 7 to 14, wherein the
surface-treating agent is at least one selected from the group
consisting of a coupling agent, an organic acid anhydride, an
anhydrous inorganic compound, and a desiccant.
16. The process according to claim 15, wherein the surface-treating
agent is at least one selected from the group consisting of a
silane coupling agent, an aluminum coupling agent, and a titanate
coupling agent.
17. The process according to claim 16, wherein the surface-treating
agent is selected from the group consisting of aluminum
isopropylate, aluminum ethylate, aluminum tris(ethylacetoacetate),
and ethylacetoacetato-aluminu- m diisopropylate.
Description
TECHNICAL FIELD
[0001] The present relates to a substantially anhydrous blowing
agent and a process for producing the same.
BACKGROUND ART
[0002] Blowing agents, such as azodicarbonamide, have been
conventionally utilized extensively for thermoplastic resins, for
example, vinyl chloride resins, polyolefin resins (polyethylene
resins, polypropylene resins, and the like), ethylene vinyl alcohol
resins, rubbers, and the like.
[0003] These blowing agents, which are usually finely powdered
compounds, have a problem that they aggregate and are solidified
with the lapse of time or under load to thereby show impaired
flowability in the step of addition to resins to cause hopper
clogging, or to thereby have impaired dispersibility into resins.
Mitigation of this solidification is desired more and more with the
recent trend toward quality improvement in foamed resins and labor
saving in the production thereof.
[0004] Techniques currently employed for overcoming the above
problem include (1) technique of adding inorganic powder particles,
such as silica, metal silicate or the like, as a solidification
inhibitor to a blowing agent, (2) technique of batchwise drying a
blowing agent for a sufficient period to thereby diminish the water
contained therein in a slight amount, and the like.
[0005] However, use of these techniques has various drawbacks.
Namely, technique (1), although effective in solidification
prevention in some degree, cannot impart the effect which lasts
beyond several months. For application to a blowing agent
comprising finer particles, inorganic powder particles should be
added in a larger amount. However, the addition of a larger amount
of the inorganic powder particles is causative of cell enlargement
during foaming, and is hence undesirable in applications where fine
cells are required. Technique (2), on the other hand, has
significantly reduced productivity because the drying requires much
time, resulting in an increased production cost. In addition,
technique (2) cannot cope with continuous production. Furthermore,
it is difficult to dry and remove the water contained in crystals
sufficiently to thereby obtain a substantially anhydrous blowing
agent. Also, effects in solidification prevention is limited.
[0006] Japanese Published Unexamined Patent Application No.
320432/92 discloses a method of adding a silane coupling agent
dissolved in a solvent to azodicarbonamide to thereby improve
flowability and dispersibility into resins. However, this method is
ineffective in sufficiently preventing solidification.
[0007] Furthermore, Japanese Published Unexamined Patent
Application No. 295872/96 discloses a method of adding an aluminum
coupling agent dissolved in a solvent to a chemically blowing agent
to thereby improve flowability and dispersibility into resins.
However, this method is also ineffective in sufficiently preventing
solidification.
DISCLOSURE OF THE INVENTION
[0008] The present inventors made intensive studies in order to
eliminate the above problems. As a result, they have found that a
substantially anhydrous blowing agent is obtained by treating a
blowing agent with a surface-treating agent capable of removing
water from the blowing agent, and optionally by heating it.
Furthermore, they found that the blowing agent thus obtained is
significantly inhibited from solidification and is exceedingly
useful as a blowing agent satisfactory in flowability,
dispersibility into resins, and the like, even after the lapse of a
prolonged period of time. The present invention has been completed
based on these findings.
[0009] That is, the present invention relates to a substantially
anhydrous blowing agent, especially a substantially anhydrous
crystalline azodicarbonamide.
[0010] Furthermore, the present invention relates to a
substantially anhydrous blowing agent obtained by treating a
blowing agent with a surface-treating agent capable of removing
water from the blowing agent.
[0011] Moreover, the present invention relates to a process for
producing a substantially anhydrous blowing agent, which comprises
treating a blowing agent with a surface-treating agent capable of
removing water from the blowing agent under conditions
substantially free of a solvent.
[0012] The substantially anhydrous blowing agent of the present
invention has been significantly improved especially in
unsusceptibility to solidification under load and in
unsusceptibility to solidification with the lapse of time. Hence,
the substantially anhydrous blowing agent is extremely free from
solidification even through long-term storage in a stacked state,
and retains for a long time the satisfactory flowability and the
satisfactory dispersibility into resins which properties are
possessed by the crystalline powder immediately after
production.
[0013] The foaming performances of the blowing agent of the present
invention are equal to those of the conventional blowing
agents.
[0014] Consequently, as a result that the substantially anhydrous
blowing agent of the present invention is provided, the fear that
blowing agent products may be solidified under load or with the
lapse of time from the production thereof to the use thereof by
users is eliminated.
BEST MODE FOR CARRYING OUT THE INVENTION
[0015] The blowing agent which can be used in the present invention
is selected from conventionally, known blowing agents. Examples
include azodicarbonamide (ADCA; decomposition temperature: about
200.degree. C.), p,p'-oxybis(benzenesulfonyl hydrazide) (OBSH;
decomposition temperature: about 160.degree. C.),
dinitropentamethylenetetramine (DPT; decomposition temperature:
about 200.degree. C.), p-toluenesulfonyl hydrazide (TSH;
decomposition temperature: about 110.degree. C.), benzenesulfonyl
hydrazide (BSH; decomposition temperature: about 95.degree. C.),
and the like.
[0016] The present invention can be advantageously applied
especially to blowing agent powders having a decomposition
temperature of 100.degree. C. or higher. Particularly, much merit
is brought about when the present invention is applied to ADCA, in
which solidification has conventionally been a serious problem.
[0017] The blowing agent in the present invention is preferably in
the form of a powder. Although the particle diameter thereof is not
particularly limited, it is generally about 1 to 50 .mu.m,
preferably about 3 to 30 .mu.m. The term "particle diameter" as
used herein means the median size determined with a laser
diffraction particle diameter distribution analyzer.
[0018] The term "substantially anhydrous" as used herein means to
have a water content lower than 0.03% by weight, preferably lower
than 0.010% by weight. The water content (% by weight) in
crystalline ADCA is herein determined by heating the crystalline
ADCA at 110.degree. C. for 2 hours while passing water-free
nitrogen gas therethrough, introducing the effluent nitrogen gas
into a Karl Fisher's water meter (trade name: MKS-1; manufactured
by Kyoto Electronics Manufacturing Co., Ltd.) prevented from
suffering water penetration thereinto from the surrounding air to
measure the amount of water contained in the nitrogen gas, and
converting this water amount into a percentage amount based on the
weight of the crystalline ADCA.
[0019] The surface-treating agent which can be used in the present
invention is one capable of removing water from a blowing agent.
Examples include compounds having the property of chemically
reacting with water and compounds having the property of adsorbing
or holding water. Specific examples include coupling agents,
organic acid anhydrides, anhydrous inorganic compounds, desiccants,
and the like.
[0020] Examples of the coupling agents include silane coupling
agents, aluminum coupling agents, titanate coupling agents, and the
like.
[0021] Examples of the silane coupling agents include
conventionally known silane coupling agents. Specific examples
include methyltrimethoxysilane, y-aminopropyl-triethoxysilane,
N-(P-aminoethyl)-y-aminopropyl-trimethoxys- ilane,
N-phenylaminomethyltrimethoxysilane, vinylmethyldiethoxysilane, and
the like.
[0022] Examples of the aluminum coupling agents include
conventionally known aluminum coupling agents. Specific examples
include aluminum isopropylate, aluminum ethylate, aluminum
tris(ethylacetoacetate), ethylacetoacetato-aluminum diisopropylate,
and the like.
[0023] Examples of the titanate coupling agents include
conventionally known titanate coupling agents. Specific examples
include isopropyl triisostearoyl titanate, isopropyl tris(dioctyl
pyrophosphate) titanate, tetraoctyl bis(ditridecyl phosphite)
titanate, bis(dioctyl pyrophosphate) hydroxyacetate titanate, and
the like.
[0024] These coupling agents can be used alone or as a mixture of
two or more thereof. Among these, preferred are aluminum coupling
agents, particularly, aluminum tris(ethylacetoacetate).
[0025] Examples of the organic acid anhydrides include
conventionally known organic acid anhydrides. Specific examples
include phthalic anhydride, succinic anhydride, glutaric anhydride,
benzoic anhydride, trimellitic anhydride, and the like. these
compounds bond to and remove water in a blowing agent, for example,
by the following mechanism:
(RCO).sub.2O+H.sub.2O.fwdarw.2RCOOH
[0026] (wherein R represents an organic acid residue).
[0027] The above coupling agents and the organic acid anhydrides
can be especially preferred because they not only have the property
of chemically reacting with water to thereby remove the water
contained in a blowing agent, but also have the property of forming
a film capable of preventing external water absorption on the
surface of the blowing agent (for example, unreacted coupling
agent, and the like).
[0028] Examples of the anhydrous inorganic compounds include known
anhydrous inorganic compounds so long as they can remove crystal
water by binding to water. Specific examples include anhydrous
magnesium sulfate, anhydrous potassium carbonate, anhydrous sodium
carbonate, anhydrous sodium sulfate, anhydrous sodium sulfite,
anhydrous magnesium carbonate, and the like. These compounds adsorb
water contained in a blowing agent and fix the adsorbed water as
crystal water, for example, by the following typical mechanism:
Na.sub.2SO.sub.4+nH.sub.2O.fwdarw.Na.sub.2SO.sub.4.nH.sub.2O
[0029] (wherein n represents an integer of 1 or more).
[0030] Examples of desiccants include conventionally known
desiccants so long as they have the property of removing water.
Specific examples include acid clay, silica gel, magnesium oxide,
calcium oxide, and the like.
[0031] In the present invention, the coupling agents, the organic
acid anhydrides, the anhydrous inorganic compounds, and the
desiccants may be used alone or as a mixture of two or more thereof
as the surface-treating agent.
[0032] Upon application to the surface of a blowing agent
and-preferably heating, the surface-treating agent efficiently
reacts with or adsorbs water contained in the blowing agent to
thereby reduce the water content of the blowing agent.
[0033] The surface-treating agent is preferably used as it is
without being dissolved in a solvent, preferably under conditions
substantially free of a solvent, in order that no adverse influence
be exerted on reaction with water or adsorption of water. If a
solution or dispersion of an coupling agent in a solvent is used,
the reaction between the water present in the blowing agent and the
coupling agent does not proceed sufficiently, water is remained in
the blowing agent, and therefore, a substantially anhydrous blowing
agent cannot be obtained. Consequently, such use is not preferred
under the mixing conditions where pulverization of a blowing agent
is inhibited. Especially, use of an organic solvent containing
water or moisture is not preferred because a water content in the
blowing agent may be increased to the contrary.
[0034] The term "under conditions substantially free of water" as
used herein means that no solvent is used or that an organic
solvent containing a water content of less than 0.1% by weight is
used in an amount equal to or less than the amount of the
surface-treating agent. In the case of using a solid
surface-treating agent, it is preferably used in the form of a fine
powder or after being melted.
[0035] The amount of the surface-treating agent per the blowing
agent varies depending on the amount necessary for allowing the
surface-treating agent to react with the water content contained in
the blowing agent. Specifically, the surface-treating agent is
generally used in an amount of 0.01 to 10 parts by weight,
preferably 0.05 to 0.5 parts by weight, based on 100 parts of the
blowing agent.
[0036] In the present invention, heating treatment is preferably
conducted during or after the addition of a surface-treating agent
to a blowing agent to thereby accelerate the reaction between the
water in the blowing agent and the surface-treating agent. In the
present invention, the heating treatment conducted during or after
the treatment of a blowing agent with a surface-treating agent is
particularly referred to as "treating and heating".
[0037] It is effective that the heating is carried out during the
addition of a surface-treating agent to a blowing agent.
[0038] In the case of using a surface-treating agent which is solid
at ordinary temperature, the surface-treating agent is preferably
subjected to preheating treatment prior to the addition thereof to
a blowing agent so that the solid surface-treating agent is brought
into a melted state.
[0039] For example, the heating temperature is generally from
30.degree. C. to the decomposition temperature of the blowing
agent, preferably from 40.degree. C. to the decomposition
temperature of the blowing agent. If ADCA, OBSH, DPT or the like
having a decomposition temperature of 150.degree. C. or higher is
used as a blowing agent, the preferred temperature is 55 to
100.degree. C. From the standpoint of reducing the heating period
to conduct the mixing even more efficiently to thereby minimize the
energy cost, it is preferred to use a heating temperature of about
70 to 90.degree. C.
[0040] Methods for adding a surface-treating agent to a blowing
agent are not particularly limited. However, a preferred method is
to spray the surface-treating agent with a pressure nozzle, a
two-fluid nozzle, or the like so as to add the surface-treating
agent in the form of fine droplets.
[0041] Also, preferably, the addition is carried out while
sufficiently mixing a blowing agent.
[0042] Mixing apparatuses which can be used for the above mixing
are not particularly limited. Examples include a supermixer, a
Henschel mixer, a screw mixer such as a Nauta mixer, a proshear
mixer, and a ribbon blender.
[0043] If a blowing agent which has been made substantially
anhydrous is pulverized, the resultant powder has an increased
specific surface area and hence enhanced hygroscopicity.
Additionally, even if the blowing agent powder which has been
coated to inhibit moisture adsorption is used, a section having no
coating is provided, and hence hygroscopicity is increased more and
more. Thus., the effect of the present invention may be lost.
Particularly, if the blowing agent powders having a particle
diameter of 10 .mu.m or more which are easily pulverized are used,
it should be especially paid attention to this point.
[0044] Accordingly, in the present invention, preferably, the
mixing is conducted under mixing conditions where pulverization of
a blowing agent is inhibited. Herein the term "under mixing
conditions where pulverization of a blowing agent is inhibited"
means that an increase in the specific surface area through the
treatment is 20% or less, more preferably 10% or less. Preferably,
as mixers satisfying the conditions, mixers used for blowing agent
powders having a particle diameter of about 10 to 300 .mu.m include
a Nauta mixer, a proshear mixer (the chopper blades are removed
before use), and the like. Furthermore, mixers used for blowing
agent powders having a particle diameter of about 3 to 10 .mu.m
which are comparatively difficult to be pulverized include a
universal mixer, a proshear mixer (the chopper blades are removed
before use), and the like. Mixers used for blowing agent powders
having a particle diameter of about 3 to 5 .mu.m which are
difficult to be pulverized include a supermixer, a Henschel mixer,
and the like. The mixing conditions where pulverization of the
blowing agent is inhibited can be provided by adjusting the rotary
number of each mixer appropriately.
[0045] In using a liquid surface-treating agent, it is preferred to
use a pressure nozzle, a two-fluid nozzle, or the like, to spray
the surface-treating agent in the form of fine droplets over a
blowing agent. By spraying a surface-treating agent as fine
droplets over a blowing agent, the blowing agent according to the
present invention can be obtained with a small amount of the
surface-treating agent.
[0046] The substantially anhydrous blowing agent of the present
invention can be advantageously used as a blowing agent for various
synthetic resins in the same manner as conventional blowing
agents.
[0047] Furthermore, the substantially anhydrous blowing agent of
the present invention can be used as a blowing agent composition
comprising the crystalline powder and one or more ingredients known
in this field, such as a stabilizer, a pigment/filler, a blowing
inhibitor, and the like. Examples of the stabilizer include
tribasic lead sulfate, dibasic phosphites, lead stearate, zinc
stearate, zinc carbonate, zinc oxide, barium stearate, aluminum
stearate, calcium stearate, dibutyltin maleate, urea, and the like.
Examples of the pigment/filler include chrome yellow, carbon black,
titanium dioxide, calcium carbonate, and the like. Examples of the
blowing inhibitor include maleic acid.
[0048] For easily understanding the present invention, a blowing
agent according to the present invention obtained using ADCA as a
blowing agent and aluminum tris(ethylacetoacetate) as a
surface-treating agent will be explained below with respect to the
effects thereof which the present inventors have ascertained.
However, the following explanation should not be construed as
limiting the scope of the invention in any way.
[0049] Powders of blowing agents, for example, ADCA, are usually
composed of microscopically porous particles, in each of which
water is present on the surface thereof and in the pores and inner
parts thereof. When such a powder of ADCA is treated with aluminum
tris(ethylacetoacetate), it is considered that the aluminum
tris(ethylacetoacetate) reacts with the water present on the
surface and in the pores of the ADCA to decompose into aluminum
hydroxide and ethyl acetoacetate, and an aluminum hydroxide film is
coated on the surface of the ADCA. If the reaction is carried out
at a temperature as low as room temperature, a long time is
required for the reaction. However, if it is heated to about
80.degree. C., the reaction is accelerated and completed shortly.
1
[0050] It is considered that not only water is removed from the
surface and pores of the powders by the above treatment, but also
the water remaining in the powders in a slight amount is inhibited
from migrating to the powder surface by the film of aluminum
hydroxide formed, whereby solidification is prevented. The aluminum
coupling agent remaining unreacted is considered to contribute to
solidification prevention due to its water repellency. If the
powder is further contacted with external water, the above reaction
proceeds gradually and water is removed so that solidification is
prevented.
EXAMPLES
[0051] The present invention will be explained below in more detail
by reference to Examples and Comparative Examples. Hereinafter, all
percents are by weight, unless otherwise indicated.
[0052] ADCA used in the following Examples was one manufactured by
Otsuka Chemical Co., Ltd. and having an average particle diameter
of 20 .mu.m.
Example 1
[0053] Twenty-five kg of ADCA placed in a cone ribbon blender
(trade name: Ribocone E RME-50; manufactured by Okawara Mfg. Co.,
Ltd.) was stirred at 70 rpm and 90.degree. C. for 10 minutes, while
adding thereto, by spraying, 50 g of aluminum
tris(ethylacetoacetate) (trade name: ALCH-TR; manufactured by
Kawaken Fine Chemicals Co., Ltd.) which had been melted by heating
at 90.degree. C. Thereafter, stirring was further continued under
the same conditions for 7.5 minutes to obtain a blowing agent
powder (crystalline ADCA) according to the present invention.
Example 2
[0054] Twenty-five kg of ADCA placed in a cone ribbon blender
(trade name: Ribocone E RME-50; manufactured by Okawara Mfg. Co.,
Ltd.) was stirred at 70 rpm and 90.degree. C. for 10 minutes, while
adding thereto 50 g of
N-(.beta.-aminoethyl)-.gamma.-aminopropyltrimethoxysilane (trade
name: TSL8340; manufactured by Toshiba Silicone Co., Ltd.) by
spraying at 90.degree. C. Thereafter, stirring was further
continued under the same conditions for 7.5 minutes to obtain a
blowing agent powder (crystalline ADCA) according to the present
invention.
Example 3
[0055] Twenty-five kg of ADCA placed in a cone ribbon blender
(trade name: Ribocone E RME-50; manufactured by Okawara Mfg. Co.,
Ltd.) was stirred at 70 rpm and 90.degree. C. for 10 minutes, while
adding thereto 50 g of glutaric anhydride by spraying at 80.degree.
C. Thereafter, stirring was further continued under the same
conditions for 7.5 minutes to obtain a blowing agent powder
(crystalline ADCA) according to the present invention.
Comparative Example 1
[0056] Twenty-five kg of ADCA was mixed with a solution of 50 g of
N-(.beta.-aminomethyl)-.gamma.-aminopropyltrimethoxy-silane (trade
name: TSL8340; manufactured by Toshiba Silicone Co., Ltd.) in 1 kg
of water by means of Supermixer (trade name; manufactured by Kawada
Seisakusho K.K.) at 600 rpm and room temperature for 10 minutes.
Thereafter, stirring was further continued for drying under the
same conditions for 7.5 minutes to obtain a blowing agent powder of
Comparative Example 1.
Comparative Example 2
[0057] Untreated ADCA was taken as a bowing agent powder of
Comparative Example 2.
Test Example 1
[0058] Each of the blowing agent powders obtained in the Examples
and Comparative Examples given above was subjected to a measurement
of water content (content of residual water), a solidification test
in stacking, and a solidification test in practical package. The
results obtained are shown in Table 1.
[0059] (1) Measurement of Water Content:
[0060] Ten g of a sample was precisely weighed out and placed in a
flask. The sample was heated at 110.degree. C., for 2 hours while
passing water-free nitrogen gas through the flask. During this
heating, the effluent nitrogen gas from the flask was introduced
into a Karl Fisher's water meter prevented from suffering water
penetration thereinto from the surrounding air (trade name: MKS-1;
manufactured by Kyoto Electronics Manufacturing Co., Ltd.) to
measure an amount of the water (g) contained in the nitrogen
gas.
[0061] The water content of the sample was calculated using the
following equation:
Water content (%)=(Amount of the water/Amount of the weighed
sample).times.100
[0062] (2) Solidification Test in Stacking:
[0063] Polyethylene bags each having dimensions of 23 cm by 13 cm
were respectively packed with 400 g of a sample. After sufficient
deaeration, the opening of each bag was heat-sealed. The packages
thus obtained were stacked, and a load of 0.08 kg/cm.sup.2 was
imposed on the stack. After 10 days, the sample was taken out and
screened with a 14-mesh sieve to measure the amount of the sample
screened out. This amount was converted to %, which was taken as
the value of solidification in stacking.
[0064] (3) Solidification Test in Practical Package:
[0065] A 25 kg portion of a sample was packed into a corrugated
fiberboard case for use as a product packaging container for
distribution. This package was allowed to stand for 1 month under
conditions at a temperature of 40.degree. C. and a humidity of 80%.
Thereafter, the sample was screened with a 14-mesh sieve to measure
the amount of the sample screened out. This amount was converted to
%, which was taken as the value of solidification in practical
package.
1 TABLE 1 Water Solidification Solidification content degree in
degree in practical (%) stacking (%) package (%) Example 1
<0.005 2.3 1.3 Example 2 <0.005 3.0 2.5 Example 3 0.010 9.8
5.0 Comparative 0.041 5.2 12.4 Example 1 Comparative 0.075 56.4
41.6 Example 2
[0066] A comparison between the test results for the crystalline
ADCA's of Examples 1 and 2 and those for the crystalline ADCA of
Comparative Example 2 shows that the anhydrous crystalline ADCA
according to the present invention were markedly more inhibited
from solidification than the untreated blowing agent powder.
[0067] A comparison between the test results for the blowing agent
powder of Example 2 and those for the blowing agent powder of
Comparative Example 1 shows that the surface treatment with a
silane coupling agent also yielded a crystalline powder of
anhydrous ADCA having greatly improved unsusceptibility to
solidification, as desired in the present invention, when no
solvent was used and heating treatment was conducted.
Test Example 2
[0068] Each of the crystalline ADCA powders obtained in Examples 1,
2, and 3 and Comparative Example 2 (provided that the crystalline
ADCA powders of Examples 1, 2, and 3 used here had been subjected
to the solidification test in stacking in Test Example 1) was
compounded in an amount of 15 parts by weight with 100 parts by
weight of low-density polyethylene (melt index: 2.0) and 0.8 parts
by weight of dicumyl peroxide. The resultant compositions each was
kneaded with heating at a roll temperature of 110 to 115.degree.
C., taken out as a sheet having a thickness of 5 mm, and then
heated at 125.degree. C. for 5 minutes while applying a pressure of
120 kg/cm.sup.2 thereto to obtain a pressed sheet. The sheets
obtained were foamed using a hot-air oven set at 220.degree. C.
[0069] The foamed materials thus obtained using the crystalline
ADCA's of Examples 1, 2, and 3 and Comparative Example 2,
respectively, each had uniform and fine cells. The foamed materials
were satisfactory and almost equal to one another in surface
smoothness and decomposition rate.
[0070] These results show that even the anhydrous crystalline ADCA
according to the present invention, which had been allowed to stand
under load for a prolonged period of time, were equal in foaming
performance to the crystalline ADCA just after production.
INDUSTRIAL APPLICABILITY
[0071] The blowing agent thus obtained is significantly inhibited
from solidification and is exceedingly useful as a blowing agent
satisfactory in flowability, dispersibility into resins, and the
like, even after the lapse of a prolonged period of time. They are
useful in the same field as blowing agents which have
conventionally been utilized extensively as blowing agents for
thermoplastic resins, for example, vinyl chloride resins,
polyolefin resins (e.g., polyethylene resins, polypropylene resins,
and the like), ethylene vinyl alcohol resins, rubbers, and the
like.
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