CA1073620A - Extrusion foamed article and process for producing the same - Google Patents
Extrusion foamed article and process for producing the sameInfo
- Publication number
- CA1073620A CA1073620A CA248,591A CA248591A CA1073620A CA 1073620 A CA1073620 A CA 1073620A CA 248591 A CA248591 A CA 248591A CA 1073620 A CA1073620 A CA 1073620A
- Authority
- CA
- Canada
- Prior art keywords
- resin
- foamed article
- weight
- weight percent
- extrusion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/36—Feeding the material to be shaped
- B29C44/46—Feeding the material to be shaped into an open space or onto moving surfaces, i.e. to make articles of indefinite length
- B29C44/50—Feeding the material to be shaped into an open space or onto moving surfaces, i.e. to make articles of indefinite length using pressure difference, e.g. by extrusion or by spraying
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2457/00—Characterised by the use of unspecified polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
Abstract
EXTRUSION FOAMED ARTICLE AND
PROCESS FOR PRODUCING THE SAME
Abstract of the disclosure An extrusion foamed article with thick and large cross-sectional area is made by extrusion foaming a mixture of an ionomer resin and a styrenic resin by use of a volatile blowing agent. The process is specific in easy and economical production of a thick foamed article and a novel foamed article having well balanced properties can be produced by this process.
PROCESS FOR PRODUCING THE SAME
Abstract of the disclosure An extrusion foamed article with thick and large cross-sectional area is made by extrusion foaming a mixture of an ionomer resin and a styrenic resin by use of a volatile blowing agent. The process is specific in easy and economical production of a thick foamed article and a novel foamed article having well balanced properties can be produced by this process.
Description
36Z~
This invention relates to a method for the extru-sion foaming of synthetic resin, which enables economical and continuous extrusion foamed ar-ticle of large and thick cross section. Further, it relates to an economical method for the manufacture o:E an extrusion foamed article of synthetic resin excelling in flexibility, cushioning property, resistance to heat and compression creep and other properties.
Methods which effect desired foaming of a poly-styrene resin, polyethylene resin, etc. by the steps of mixing the resin with a blowing agent, heating and kneadin~
the mixture and extruding the resultant molten mixture into a zone of decreased pressure enjoy a wiaespread acceptance.
With these techniques for the extrusion foaming of synthe-tic resins, however, foamed article,having large and thick cross section cannot easily be obtai.ned. If foamed article of large thickness are to be produced at all under speci.al conditions, such conventional techniques have inevitably found it necessary to use a complicated processing system .
' 20 and an extruder having a high extruding capacity and a '' large screw diameter, inconveniencing the operation.
. If a cylinder-shaped extrusion foamed article of about 150 mm in diameter is to ~e obtained by extrusion foaming a low-denqity polyethylene resin, for example, it is found necessary to use a large extruder of at least ' 60 mm in screw diameter. The difficulties experienced in :~ the adjustment of extruding conditions ow.ing to the , lar~eness of the size of extruder either result in impair : uniformity of cell diameter or cell distribution or necessitate use of complicate facillties or ski.iled ,. bm.
.:
.
"~ fi20 manual manipulation for the adjus-tment of said conditions.
If the foamed article is used as a heat insulat-ing material, cushioning material, etc., for example, it is required to excel in various properties such as cell porosity, recovery from compression, resistance to heat and compression creep and thermal conductivity and to have the numerical values of these properties invariably exceed certain levels in concert. In this sense, all the extrusion foamed articles obtainable by the existing techniques are not satisfactory. For this reason, the conventional techniques have su~fered from a disadvantage that the particular resin subjected to a given extrusion foaming should be selected very strictly so as to meet finely defined use conditions. Foamed articles of a polystyrene resin, for example, have the disadvantage that they are deficient in flexibility and ability to absorb repeated impacts, although they are excellent in compressive ~ .
strength and thermal insulating property. In the case of the extrusion foamed article of a low-density polyethylene resin, for example, there is a disadvantage that the article is defici~nt in thermal-insulatin~ property and in resistance to heat and compression creep despite its excellency in flexibility and cushioning property. The extrusion foamed article of an ionic copolymer (hereinafter referred to as l'ionomer") resin is claimed to excel in cushioning property and yet suffers from a disadvantage that it shows notable deficiency in resistance to heat and compression creep, compressive strength, etc. Besides this drawback, it has a fault that the extrusion back pressure at the time of extrusion foaming is abnormally ' ' ~ 3 ~
bm.
,~
: ' ~0736Z~
high so as not to enable the extrusion foaming to be economically accomplished.
Numerous researches have been carried out with a view to developing extrusion foamed articles of improved properties by mixing two or more types of synthetic resins and foaming the resultant resin blends. Unfortunately, however, the techniques which have issued from such researches cannot be called perfect since the plurality of types of resins involved have no sufficient compati-`' 10 bilityO
For example, the method disclosed by Japanese Patent Laying-open Nos. 35471/1974 and 25675/1975, namely a method which comprises the steps of preparinq a basal resin by use of 60 to 90 parts by weight of a polyolefin resin and 10 to 40 parts by weight of a polystyrene resin, mixing this basal resin with a blowing agent (particularly 'l of trichlorofluoromethane) and extrusion foaming the , mixture, has a disadvantage that the foaming effected thereby suffers from heavy shrinkage, the method fails to permit economic production of a foamed article having large and thick cross section, and the cushioning property exhibited by the article is of a level too 1QW for the product to be rendered practicable.
The present ivention has originated in such status of affairs. Its perfection has resulted from the conception of the combination of resins which show notably inferior compatibility to a combination of polyethylene and polystyrene and which discoura~e everyone from givin~
due attention thereto, namely, the organic combination of the three requirements indicated below:
`.'` .
,,,~, bm.
~ .
3fi2~ ~
(1) A proper amount of an ionomer resin which shows inferior compatibility with polyolefins, and (2~ a proper amoun~ of a styrenic resin which shows inferior compatibility with said polyolefins and said ionomer (3) can be extrusion foamed in the presence of a volatile blowing agent (of a type to be specified as occasion demands).
An object of the present invention is to provide an economical method for extrusion foaming, which is capable of easily extrusion foaming of high quality and large and ~hick cross section by use of an extruder of a small screw diameter.
Another ob~ect of the present invention is to provide a novel extrusion foamed article of synthetic resin, novel in the sense that the numerical values of the properties a ~oamed article is required to possess for use in thermal insulating materlals, cushioning materials, etc. invariably exceed certain fixed levels.
In one particular aspect the present invention provides a process for producing a foamed article which comprlses blending 10 to 90% by weight of an ionomer resin having a melt index from 0.1 to 50 g/10 min. and 90 to 10% by weight of a styrenic synthetic resin, and mixing 100 parts by weight oE the resulting blend in the molten state with 5 to 60 parts by weight of a volatile blowing agent, having a Kauri-butanol value up to 25, in an extruder at high temperature and pressure, and extruding the resulting blended mixture into a ~one kept under a pressure which is not higher than atmospheric pressure, thereby allowing the extruda~e to expand.
In another particular aspect the present invention provides a foamed article having a bulk density from 15 to 200 kg/m3 comprising a foamed resinous composition containing 10 to 90 weight percent of an ionomer resin having a melt index of from 0.1 to 50 g/10 min. and 90 to 10 weight percent of a styrenic jr ~ ~ ~ 5-:~73~
synthetic resin.
In the accompanying drawings, Figure 1 shows a schematic drawing of the distribution of cells of the product of this ; invention;
Figure 2 an enlarged view of Figure 1;
Figure 3 a schematic drawing of the distribution of cells in the product of prior art;
Figure 4 an enlarged view of Figure 3, respectively.
.; To accomplish the objects described above according to the present invention, the present invention provides a process for producing a foamed articl of synthetic resin, which comprises blending 100 parts by .. .
. ~
":
., . ~ .
~' . . . .
'.' .
.~ .
~. 30 ., .
.' .
~ 5a-... . . .
'.: ' . .. : ~ .
0~36Z~
weight of a molten resin mixture consisting of 10 to 90 weight percent of ionomer resin and 90 to 10 weight ; percent of a styrenic synthetic resin with 5 to 60 parts by weight of a volatile blowing agent at an elevated temperature under increased pressure, extruding the result-ant mixture into a zone of a pressure not higher than atmospheric pressure, thereby allowing the extrudate to expand.
In the first place, the essential requirement for the present invention resides in using as one component of the basal resin an ionomer resin and as the other compo-nent thereof a styrenic resin. This particular combination of the components has been singled out on a very strict -criterion from among a host of possible combinations of synthetic resins. E~pec~al~y when the compatibility is taken into account, it is a surprising and hardly imagin-able thing even for a person of ordinary skill in the art that the two components mix so thoroughly with each other as to give rise to an extrusion foamed article of uniform texture and, moreover, the resin blend resulting from said mixture enjoys improved extrusion foaming property.
The ratio of the ionomer resin to the styrenic resin which is advantageous for this invention is 10 to 90 percent, preferably 30 to 90 percent, of the ionomer resin to 90 to 10 percent, preferably 70 to 10~ o~ the styrenic resin. If the proportion of the ionomer resin exceeds the upper limit 90 percent, the back pressure at the time of extrusion abnormally increases to the extent of . .
rendering the commercial production of extrusion foamed article impracticable unless the volume of extrusion is ,,~
"
bm.
'.~J, ~''' ~ ' ' ' ' ,'.
., . . , ~ ' . .
~3620 '' lowered or there is developed and employed a pressure proof extruder of a special design. If the proportion of 'the ionomer resin fails to exceed the lower limit of 10 percent, the quality of the styrenic resin predominates over that of the ionomer resin and the compatihility between the components is adversely affected, with a disadvantageous result that the extrusion foaming property of the resin blend will be degraded.
As measured in terms of the crass section of extrusion foamed article prepared under the optimum conditions of a ~iven extruder, the moldability improved by the blending of the two components mentioned above is about five times as large as that obtained in the extrusion of a low-density polyethylene resin and 'about two times as large as that obkained in the extrusion of a styrenic resin.
Further, the back pressure involved in the extrusion by the method of this invention is 40 to 60 percent less than that involved in the extrusion of the ionomer res~in.
The term "ionomer resin" as used in the present invention refers to a copolymer which is 'obtained when represented by the following generic formula:
RI I ~ R" R ~ R~ R ~ R"
~CHCH2~a ~CH ~b ~ H-l~C -~CH f ~d wherein R denotes hydrogen atom or an alkyl group; each of R~ and R" denotes hydrogen atom or a methyl group; R"
denotes a lower alkyl group such as methyl, ethyl or propyl; M denotes a metal as is described below, and a, b, c and d den~t~ mol percentages of the respective monomers ; 30 in the copolymer, and a is 50 mol % or more, b, c and d .
; bm.
.
36~0 are determined from neutrality N which is 60 mol percent or less and the saponification degree which is 50 mol percent or more.
With respect to the ionomer resin of the foregoing description, the neutrality N and the saponification de~ree S will be as defined below.
7,,, N (mol percent) = c x 100 S (mol percent) = c + d x 100 b + c + d In the present invention, the extrusion foamed article produced thereby acquires discrete cells of a -uniform size more readily when the neutrality N of the -~
copolymer in use does not exceed 60 percent. More prefer-ably, N is in -the range from 10 to 40 percent. The saponifi-cation degree S is only required to exceed 50 percent. For the copolymer to enjoy uniform foaming more readily, however, the saponification degree of the copolymer in use is desired to be from 70 to 100 percent.
The sum of c ~ d is preferably in the range of from 0.2 to 25 mol percent, most preferably in the range : . .
of from 1 to 10 mol percent.
The ionomer resin, in its solid state, is ionically ;., . , crosslinked. When it is brought into a molten state, said crosslinked will disappear or decrease in number. When it is ; bxought back into its solid state~, it is ionically cross-~inked again.
' To be more specific about the metal ion component , of said copolymer, it is the ion of any of the metals, 1 to ,~"~
~i~ 3 in valency, belonging to groups I, II, III, IV-a and VIII
.~
in the Periodic Table of Elements. Examples of the monovalent ?.~
, .~.,.
~'' bm.
,...................... .
.,.. ~. I , ."," . ~ . , . ., , .. - , , . , , . ,; ,:
~~ l0~3~a metal ions include Na , K , Li , Ag and CU ~ Examples of the divalent metal ions include Be , Mg , Ca , Sr , Ba Cu +, Cd++, Sn+ , Pb , Fe , Co , Ni and Zn . And examples of the trivalent metal ions include Sc , Fe ++~
and Yt . For the purpose of the present invention, the metal ion is desired to be Na , Zn , or Ca - The processes disclosed in U.S~ Patents 3,264,272 and 3,789,035 can be applicable for preparation of the ionomers as mentioned above.
The ionomer resin, in its solid state, retains ; an ionic crossed linkage, When it is brought into a molten state, said crossed linkage ceases to exist or decreases~
When it is brought back into its solid state, it regains said crossed linkage~
The value of the MI (as determined by the method, Condition E, specified by ASTM-D-1238-70) of the ionomer resin suffices in the range of from 0,1 to 50 g/10 minutes.
The copolymer produces uniform foaming more readily when ;; the MI thereof falls in the range of from 0,3 to 10 g/10 minutes, most preferably from 0.3 to 2.9 g/10 minutes~
; When the MI exceeds the upper limit 50 g/10 minutes, the extrusion foamed article produced from the copolymer fails to acquire discrete ce~ls of a uniform size and consequently suffers from degradation oE both com~ressive strength and cushioning property, The extrusion Eoamed article likewise fails to acquire discrete cells of a uniform size when the MI of the copolymer does not reach the lower limit 0,1 g/10 minutes, The term "styrenic resin" as used in the specification and claims refers to a synthetic polymeric . ~, .
. ~ ' .' .
~ 9 ~
bm:p'~
. ' ' ~3~2~
resin containing at least 20 wt.% o~ styrene or styrene derivative. The following groups of polymeric resins are included:
(1) homopolymers of styrene or styrene derivative such as
This invention relates to a method for the extru-sion foaming of synthetic resin, which enables economical and continuous extrusion foamed ar-ticle of large and thick cross section. Further, it relates to an economical method for the manufacture o:E an extrusion foamed article of synthetic resin excelling in flexibility, cushioning property, resistance to heat and compression creep and other properties.
Methods which effect desired foaming of a poly-styrene resin, polyethylene resin, etc. by the steps of mixing the resin with a blowing agent, heating and kneadin~
the mixture and extruding the resultant molten mixture into a zone of decreased pressure enjoy a wiaespread acceptance.
With these techniques for the extrusion foaming of synthe-tic resins, however, foamed article,having large and thick cross section cannot easily be obtai.ned. If foamed article of large thickness are to be produced at all under speci.al conditions, such conventional techniques have inevitably found it necessary to use a complicated processing system .
' 20 and an extruder having a high extruding capacity and a '' large screw diameter, inconveniencing the operation.
. If a cylinder-shaped extrusion foamed article of about 150 mm in diameter is to ~e obtained by extrusion foaming a low-denqity polyethylene resin, for example, it is found necessary to use a large extruder of at least ' 60 mm in screw diameter. The difficulties experienced in :~ the adjustment of extruding conditions ow.ing to the , lar~eness of the size of extruder either result in impair : uniformity of cell diameter or cell distribution or necessitate use of complicate facillties or ski.iled ,. bm.
.:
.
"~ fi20 manual manipulation for the adjus-tment of said conditions.
If the foamed article is used as a heat insulat-ing material, cushioning material, etc., for example, it is required to excel in various properties such as cell porosity, recovery from compression, resistance to heat and compression creep and thermal conductivity and to have the numerical values of these properties invariably exceed certain levels in concert. In this sense, all the extrusion foamed articles obtainable by the existing techniques are not satisfactory. For this reason, the conventional techniques have su~fered from a disadvantage that the particular resin subjected to a given extrusion foaming should be selected very strictly so as to meet finely defined use conditions. Foamed articles of a polystyrene resin, for example, have the disadvantage that they are deficient in flexibility and ability to absorb repeated impacts, although they are excellent in compressive ~ .
strength and thermal insulating property. In the case of the extrusion foamed article of a low-density polyethylene resin, for example, there is a disadvantage that the article is defici~nt in thermal-insulatin~ property and in resistance to heat and compression creep despite its excellency in flexibility and cushioning property. The extrusion foamed article of an ionic copolymer (hereinafter referred to as l'ionomer") resin is claimed to excel in cushioning property and yet suffers from a disadvantage that it shows notable deficiency in resistance to heat and compression creep, compressive strength, etc. Besides this drawback, it has a fault that the extrusion back pressure at the time of extrusion foaming is abnormally ' ' ~ 3 ~
bm.
,~
: ' ~0736Z~
high so as not to enable the extrusion foaming to be economically accomplished.
Numerous researches have been carried out with a view to developing extrusion foamed articles of improved properties by mixing two or more types of synthetic resins and foaming the resultant resin blends. Unfortunately, however, the techniques which have issued from such researches cannot be called perfect since the plurality of types of resins involved have no sufficient compati-`' 10 bilityO
For example, the method disclosed by Japanese Patent Laying-open Nos. 35471/1974 and 25675/1975, namely a method which comprises the steps of preparinq a basal resin by use of 60 to 90 parts by weight of a polyolefin resin and 10 to 40 parts by weight of a polystyrene resin, mixing this basal resin with a blowing agent (particularly 'l of trichlorofluoromethane) and extrusion foaming the , mixture, has a disadvantage that the foaming effected thereby suffers from heavy shrinkage, the method fails to permit economic production of a foamed article having large and thick cross section, and the cushioning property exhibited by the article is of a level too 1QW for the product to be rendered practicable.
The present ivention has originated in such status of affairs. Its perfection has resulted from the conception of the combination of resins which show notably inferior compatibility to a combination of polyethylene and polystyrene and which discoura~e everyone from givin~
due attention thereto, namely, the organic combination of the three requirements indicated below:
`.'` .
,,,~, bm.
~ .
3fi2~ ~
(1) A proper amount of an ionomer resin which shows inferior compatibility with polyolefins, and (2~ a proper amoun~ of a styrenic resin which shows inferior compatibility with said polyolefins and said ionomer (3) can be extrusion foamed in the presence of a volatile blowing agent (of a type to be specified as occasion demands).
An object of the present invention is to provide an economical method for extrusion foaming, which is capable of easily extrusion foaming of high quality and large and ~hick cross section by use of an extruder of a small screw diameter.
Another ob~ect of the present invention is to provide a novel extrusion foamed article of synthetic resin, novel in the sense that the numerical values of the properties a ~oamed article is required to possess for use in thermal insulating materlals, cushioning materials, etc. invariably exceed certain fixed levels.
In one particular aspect the present invention provides a process for producing a foamed article which comprlses blending 10 to 90% by weight of an ionomer resin having a melt index from 0.1 to 50 g/10 min. and 90 to 10% by weight of a styrenic synthetic resin, and mixing 100 parts by weight oE the resulting blend in the molten state with 5 to 60 parts by weight of a volatile blowing agent, having a Kauri-butanol value up to 25, in an extruder at high temperature and pressure, and extruding the resulting blended mixture into a ~one kept under a pressure which is not higher than atmospheric pressure, thereby allowing the extruda~e to expand.
In another particular aspect the present invention provides a foamed article having a bulk density from 15 to 200 kg/m3 comprising a foamed resinous composition containing 10 to 90 weight percent of an ionomer resin having a melt index of from 0.1 to 50 g/10 min. and 90 to 10 weight percent of a styrenic jr ~ ~ ~ 5-:~73~
synthetic resin.
In the accompanying drawings, Figure 1 shows a schematic drawing of the distribution of cells of the product of this ; invention;
Figure 2 an enlarged view of Figure 1;
Figure 3 a schematic drawing of the distribution of cells in the product of prior art;
Figure 4 an enlarged view of Figure 3, respectively.
.; To accomplish the objects described above according to the present invention, the present invention provides a process for producing a foamed articl of synthetic resin, which comprises blending 100 parts by .. .
. ~
":
., . ~ .
~' . . . .
'.' .
.~ .
~. 30 ., .
.' .
~ 5a-... . . .
'.: ' . .. : ~ .
0~36Z~
weight of a molten resin mixture consisting of 10 to 90 weight percent of ionomer resin and 90 to 10 weight ; percent of a styrenic synthetic resin with 5 to 60 parts by weight of a volatile blowing agent at an elevated temperature under increased pressure, extruding the result-ant mixture into a zone of a pressure not higher than atmospheric pressure, thereby allowing the extrudate to expand.
In the first place, the essential requirement for the present invention resides in using as one component of the basal resin an ionomer resin and as the other compo-nent thereof a styrenic resin. This particular combination of the components has been singled out on a very strict -criterion from among a host of possible combinations of synthetic resins. E~pec~al~y when the compatibility is taken into account, it is a surprising and hardly imagin-able thing even for a person of ordinary skill in the art that the two components mix so thoroughly with each other as to give rise to an extrusion foamed article of uniform texture and, moreover, the resin blend resulting from said mixture enjoys improved extrusion foaming property.
The ratio of the ionomer resin to the styrenic resin which is advantageous for this invention is 10 to 90 percent, preferably 30 to 90 percent, of the ionomer resin to 90 to 10 percent, preferably 70 to 10~ o~ the styrenic resin. If the proportion of the ionomer resin exceeds the upper limit 90 percent, the back pressure at the time of extrusion abnormally increases to the extent of . .
rendering the commercial production of extrusion foamed article impracticable unless the volume of extrusion is ,,~
"
bm.
'.~J, ~''' ~ ' ' ' ' ,'.
., . . , ~ ' . .
~3620 '' lowered or there is developed and employed a pressure proof extruder of a special design. If the proportion of 'the ionomer resin fails to exceed the lower limit of 10 percent, the quality of the styrenic resin predominates over that of the ionomer resin and the compatihility between the components is adversely affected, with a disadvantageous result that the extrusion foaming property of the resin blend will be degraded.
As measured in terms of the crass section of extrusion foamed article prepared under the optimum conditions of a ~iven extruder, the moldability improved by the blending of the two components mentioned above is about five times as large as that obtained in the extrusion of a low-density polyethylene resin and 'about two times as large as that obkained in the extrusion of a styrenic resin.
Further, the back pressure involved in the extrusion by the method of this invention is 40 to 60 percent less than that involved in the extrusion of the ionomer res~in.
The term "ionomer resin" as used in the present invention refers to a copolymer which is 'obtained when represented by the following generic formula:
RI I ~ R" R ~ R~ R ~ R"
~CHCH2~a ~CH ~b ~ H-l~C -~CH f ~d wherein R denotes hydrogen atom or an alkyl group; each of R~ and R" denotes hydrogen atom or a methyl group; R"
denotes a lower alkyl group such as methyl, ethyl or propyl; M denotes a metal as is described below, and a, b, c and d den~t~ mol percentages of the respective monomers ; 30 in the copolymer, and a is 50 mol % or more, b, c and d .
; bm.
.
36~0 are determined from neutrality N which is 60 mol percent or less and the saponification degree which is 50 mol percent or more.
With respect to the ionomer resin of the foregoing description, the neutrality N and the saponification de~ree S will be as defined below.
7,,, N (mol percent) = c x 100 S (mol percent) = c + d x 100 b + c + d In the present invention, the extrusion foamed article produced thereby acquires discrete cells of a -uniform size more readily when the neutrality N of the -~
copolymer in use does not exceed 60 percent. More prefer-ably, N is in -the range from 10 to 40 percent. The saponifi-cation degree S is only required to exceed 50 percent. For the copolymer to enjoy uniform foaming more readily, however, the saponification degree of the copolymer in use is desired to be from 70 to 100 percent.
The sum of c ~ d is preferably in the range of from 0.2 to 25 mol percent, most preferably in the range : . .
of from 1 to 10 mol percent.
The ionomer resin, in its solid state, is ionically ;., . , crosslinked. When it is brought into a molten state, said crosslinked will disappear or decrease in number. When it is ; bxought back into its solid state~, it is ionically cross-~inked again.
' To be more specific about the metal ion component , of said copolymer, it is the ion of any of the metals, 1 to ,~"~
~i~ 3 in valency, belonging to groups I, II, III, IV-a and VIII
.~
in the Periodic Table of Elements. Examples of the monovalent ?.~
, .~.,.
~'' bm.
,...................... .
.,.. ~. I , ."," . ~ . , . ., , .. - , , . , , . ,; ,:
~~ l0~3~a metal ions include Na , K , Li , Ag and CU ~ Examples of the divalent metal ions include Be , Mg , Ca , Sr , Ba Cu +, Cd++, Sn+ , Pb , Fe , Co , Ni and Zn . And examples of the trivalent metal ions include Sc , Fe ++~
and Yt . For the purpose of the present invention, the metal ion is desired to be Na , Zn , or Ca - The processes disclosed in U.S~ Patents 3,264,272 and 3,789,035 can be applicable for preparation of the ionomers as mentioned above.
The ionomer resin, in its solid state, retains ; an ionic crossed linkage, When it is brought into a molten state, said crossed linkage ceases to exist or decreases~
When it is brought back into its solid state, it regains said crossed linkage~
The value of the MI (as determined by the method, Condition E, specified by ASTM-D-1238-70) of the ionomer resin suffices in the range of from 0,1 to 50 g/10 minutes.
The copolymer produces uniform foaming more readily when ;; the MI thereof falls in the range of from 0,3 to 10 g/10 minutes, most preferably from 0.3 to 2.9 g/10 minutes~
; When the MI exceeds the upper limit 50 g/10 minutes, the extrusion foamed article produced from the copolymer fails to acquire discrete ce~ls of a uniform size and consequently suffers from degradation oE both com~ressive strength and cushioning property, The extrusion Eoamed article likewise fails to acquire discrete cells of a uniform size when the MI of the copolymer does not reach the lower limit 0,1 g/10 minutes, The term "styrenic resin" as used in the specification and claims refers to a synthetic polymeric . ~, .
. ~ ' .' .
~ 9 ~
bm:p'~
. ' ' ~3~2~
resin containing at least 20 wt.% o~ styrene or styrene derivative. The following groups of polymeric resins are included:
(1) homopolymers of styrene or styrene derivative such as
2-methyl styr~ne, (o-, m-, p-) methyl styrene or aromatic styrene;
(2) copolymers of styrene or styrene derivative with other comonomers such as a vinyl monomer (e.g. methyl methacrylate, acrylonitrile, etc.) or a conjugated diene monomer (e.g. butadiene);
(2) copolymers of styrene or styrene derivative with other comonomers such as a vinyl monomer (e.g. methyl methacrylate, acrylonitrile, etc.) or a conjugated diene monomer (e.g. butadiene);
(3) rubber-reinforced styrene polymers or copolymers.
Typical examples of such polymers include poly-styrene, styrene-acrylonitrile copolymer and styrene-malèic anhydride copolymer, so called high-impact polystyrene and high-impact acrylonitrile-butadiene-styrene copolymer (~BS
resin).
It has been confirmed that an extrusion foamed article of thermoplastic resin containing uniform, discrete cells and excelling in compressive strenqth, cushioning property and foaming property is obtained when there is used a styrenic resin containing 3 to 80 weight percent, ;~ preferably 5 to 50 weight percent, of a rubbery substance.
The rubber-reinforced resin used for the present invention is a thermoplastic resin which contains either a diene-type monomer or polymer. Examples o~ the resin are resins such as styrene-butadiene block copolymers (e.g. so called thermoplastic) and styrene-butadiene random copolymers ~- which are obtained by the chemical reaction of a styrene monomer or polymer with a diene-type monomer or polymer, mechanically mixed resins consisting of styrene homopolymers ' bm.
36~
or styrene-based copolymers and diene-type polymers having a rubbery state at normal room temperature. The resins may be used singly or in -the form of mixtures.
As to the melt flow property of the styrenic resin used for the present invention, the MI of said resin is desired to fall in the range of from 0.3 to 30 as deter mined by the method, Condition G, specified by ASTM-D-1238-70.
~ Selection of the blowing agent for use in t~e - 10 present invention is also important. The selection can advantageously be made by taking into account the K~B.
value which will be defined afterward. Generally, there : is used a volatile blowing agen~ having a K.B. value of not more than 25 and a boiling point of not more than 90~C
under normal pressure. The upper limit 25 of the K.B. value is critical because the extrudability aimed at is not ' obtained when a volatile blowing agent having a K.B. value : ,.
exceeding 26 i8 used alone. Concrete examples of such volatile blowing agents are dichlorodifluoromethane (herein ~ 20 after referred to as F-12) (K.B. value 18, boiling point ; -29.8C under normal pressure), monochlorodifluoromethane (hereinafter referred to as F-22) ~K.B. value 25, boiling point ~40.8C), dichlorotetrafluoroethane (hereinafter referred to as F-114) (K.B. value 12, boiling point 3.8C), propane (K.B~ value 23, boiling point -42.1C) and butane (~C.B. value 24, boiling point -0.5C). These volatile blowing agents may be used either singly or in the form of mixtures consisting of two or more members.
In order to ob-tain favorable properties of the extrusion foamed article, it is preferred to use a mixture '. ' `- '-'.
.~ ~
bm.
~ .
: . . . . ~ .... . . . .
,-'' lOq36Z~
which consists of 20 to 90 weight percen-t of at least one member selected from the group of volatile blowing agents possessed of K.B. values of not more than 25 (hereinafter referred to as "group I") and 80 to 10 weight percent of at least one member selected from the group of volatile blowing agents possessed of K~B. values of not less than 26 and boiling points of not more than 90C under normal pressure (hereinafter referred to as "group II"). Although the mixing ratio of these groups I and II is variable with i .-the properties of the particular agents to be actually used, it constitutes an essential requirement for perfect accomplishment of the object of the present invention.: .
Concrete examples of volatile blowing agents of said group II include trichloromonofluoromethane (herein-after referred to as F-ll) (K.B. value 60, boiling point 23.8C under normal pressure), dichloromonofluoromethane ..
(hereinafter referred ~o as F-21) (K~B. value 102, boiling point 8.9~)~ trichlorotrifluoroethane (hereinafter referred : to as F-113) (K.B. value 32, boiling point 47.6C), methyl ch.loride (hereinafter referred to as "MeCQ") (K.B. value 80, boiling point -23.6C), methylene chloride (hereinafter referred to as "MeCQ2") (K.B. value 136, boiling point 40C), pentane (K.B. value 127, boiling point 36.1C) and hexane (K.B. value 30, boiling point 68.~C).
The amount of the blowing agent to be used in the present invention is generally in the range of from 5 to 60 parts by weight and, in case where the effectiveness of the blowing agent demands due attentlon, in the range ; of from 5 to 35 parts by weight based on 100 parts by weight : 30 of the basal resin. It may freely be selected within the ' ' .
- 12 - .
' ' . bm.
:
. .
``` 1~7362Q
~ range so as to satisfy the foaming ahility of the blowing ~ agent and the bulk density which the finally produced foamed article is intended to possess.
If the amount of the volatile blowing agent does not reach the lower limit 5 parts by weigh-t based on 100 --- parts by weight of the basal resin, then the foamed article .. . .
- ~ - consequently obtained fails to acquire uniform cells. If ~ it exceeds the upper limit 60 parts by weight, then the ~- .- ~ --:-~ - cells being formed in the course of continuous foaming are .L0 ruptured, making it impossible to provide continued produc-~ tion of extrusion form having discrete cells of a uniform :.: "' - ' size.
The basal resin of the present invention, as occasion demands, may have incorporated in its component resins or resin blend an effective amount of a stabilizer ;~ serving to repel the action of heat or light or prevent , degradation, an additive useful for enhancing smoothness and impact resistance or a coloriny agent. At the time ~ of extrusion foaming, a suitable amount of a substance ;~ 20 such as, for example, an inorganic carbDnate, organic silicate, inorganic phosphate, metal salt of higher fatty acid, or indigo which is generally used as the nucleic agent, or stabilizing agent may be used additionally for the purpose of adjusting and stabilizing the cell diameter, cell distribution and foaminc~ conditibn. Furthermore, other thermosplastic resins such as polyethylene or rubbery substances can also be used as additives, if necessary.
Also for the purpose of adjusting the cell dia-meter of the foam, an organic nucleic agent ~such as, for example, calcium stearate or barium stearate) and/or , :.; .
bm.
, ~
362~
inorganic n~lcleic agent (such as, for example, talc) may be used in the ordinarily accepted amount.
For practice of the invention, there can be used conventional technique of extrusion foaming which enjoys favorable acceptance for commercial application because of its advantageous productivity. The operational procedure usually comprises the steps of mixing a basal resin and a volatile blowing agent in an extruder at elevated tempera-tures under increased pressure, then cooling the resultant 0 blend for thereby lowering both pressure and temperature to respective levels proper for foaming and subsequently extruding the cooled blend through a die possessed of a desired shape into the atmosphere for thereby causing continuous ~oaming of the extruded blend.
For uniform dispersion of the volatile blowing agent in the basal resin, it is an absolute ~lecessity that said basal resin and volatile blowing agent be blended at elevated temperatures under increased pressure w~thin the extruder. Without uniform dispersion, it is hard to obtain advantageous foaming. At low temperatures, there is a possibility that sufficient blending of the resin and the blo~in~ agent will no longer occur. Furthermore, thexe is , also a possibility that the extrudability of the blend as observed at the time of extrusion foaming will be spoiled.
In addition, the uniformity of distribution of cells in the foamed article will be impaired. Accordingly, the properties of the foamed article will be de~rade~.
Further, at low temperatures, since the viscosity of the .;
. resin is heightened, it becomes necessary to adopt a ~1 30 complicate and expensive extruder of a special structure ;; :
bm.
.
.: ' ' ' -~ ~07~
capable of withstanding the added load and pressure exerted for the actions of extrusion and blending, rendering the commerical production disadvantageous. Under insuf-ficient pressure, there tends to ensue a disadvantage that the blow-ing agent is not uniformly distributed throughout the resin.
In the method of this invention, the temperature and pressure conditions under which the blending is càrried out within the extruder are desired to be such that, in the metering zone or mixing zone of the leading-end portion of ~ 10 the extruder in which the resin and the blowinq a~ent are ; blended more thoroughly than elsewhere, the temperature will fall in the range of from 120 to 300C and the pressure in the range of from 50 to 250 kg~cm , respectively.
` To ensure advantageous foaming, the uniform blend which has been formed under conditions of elevated tempera~
tures and increased pressure must be cooled so that its ; temperature and pressure will both be lowered to levels proper for the desired foaming.
If the blend is extruded in its uncooled state into the atmosphere, there is a fair possibility that the blend will suffer from impaired extrudability which entails disadvantages such as shrinkage of foamed article, loss of surface smoothness and failure to keep a desired shape, for example. There is also a possihility that the individual cells will be heavily ruptured to greatly degrade ~arious properties of the foamed articles. If the blend is suffered to remain under said increased pressure, then it is ex- ;~
tremely difficult to provide desired foaming of the blend and there tends to ensue a disadvantaqe that the individual cells will be heavily ruptured. If the pressure exerted . ' ' bm.
, .: .
'?~
, , . . , :: . . - :. .
~ iO~62~
: , .
on the blend is excessively lowered immediately before the blend is extruded into the atmosphere, there readily ensues a disadvantage that the individual cells will be ruptured to a notable extent. To be more specific, if the extrusion foaming is carried QUt under a pressure lower than the pressure required for liquefying the blowing agent contained ; in the blend, foaming occurs within the foaming unit before the blend is released into the atmosphere, making it difficult to provide the operation and effect of improving the extrudability of the blend and uniformizing the dis-; tribution of discrete cells in the foamed ar-ticle through advantageous utili~tion of the latent heat of evaporation ;~ involved when the blowing agent is vaporized and allowedi . .
~ to fulfill its intended function. Consequently, a dis~
7'-' advantage tends to ensue that the foamed article will have ùnuniform distribution of cells and the individual cells ~; will readily be ruptured.
i j~ ,. . ..
For the purpose of the method of this invention~
the temperature of the blend which is about to be released from the foaming unit into the atmosphere is desired to fall ,;;, .
in the range of from 70 to 110C, preferably from 85 to 100C. Desirably a rotary temperature regulator may be disposed between the extruder and the die so as to enable the temperature and pressure of the blend to be adjusted to proper levels for extrusion foaming.
If, in the method of this invention, there is used a chemical blowing agent (such as, for example, azo-dicarbonamide) which libera-tes upon thermal decomposition a foaming gas such as nitrogen or carbon dioxide which has a very low boiling point and is difficultly miscible with , . .
bm.
. ~
.'~ ' : . ,, ' . ' . . :
3~20 the basal resin, it becomes aifficult to maintain a pressure proper for foaming at the temperature proper for the foamin$
of the basal resin, and the blowing agent itself tends to vaporize within the foaming unit before the blend is r~leased into the atmosphere~ Consequently t there is involved a disadvantage that desirable foaming will no longer be obtained and the distribution of cells in the foamed article will be degraded. There~ore, such a chemical blowing agent is excluded from the scope of the invention.
The method of this invention allows the tempera-ture of the blend to fall in the range of from 70 to 110C
immediately before extrusion foaming. No other method so far developed for the manufacture of a thermoplastic resin foamed article tolerates such a broad temperature range.
This broad temperature range may well be called epochal in the sense that it permits easy commercial production of the , , foam.
For the purpose of the method of this invention, it suffices to have the blend simply released into the atmosphere. h7hen necessary, however, there may be adopted a special device which is capable of keeping the released blend under decreased pressure to the lower limit of 0~2 atm.
According to preferred embodiments, extrusion is performed under conditions such that the extrudate has a thickness ranging from 0.5 to 100 mm, more preferably from 2 to 50 mm and is allowed to an expansion ratîo of from 2 to 50 to produce a foamea article having a thickness of from 1 to 1000 mm, more preferably from 20 to 1000 mm.
The foamed article obtained according to the bm.
.
.
~736~o process of the present invention is found to be ~pecific in having well balanced properties and therefore can be used for a great v~riety of uses, Typically, foa~ed articles having thickness of 2Q mm to 1000 mm, preferably 30 to 500 mm, and bulk density of Z0 to 5~ Kg/m3 produced from a resinous mixture consisting of 40 to 70 wt.~, preferably 45 to 60 wt.%, of an ionomer resin and 60 to 30 wt~, preferably 55 to 40 wt.~ of a styrenic resin containing at least 70 wt.% of styrene or styrene derivative are unexpectedly found to be endowed with all of the following properties: (as measured by the methods as hereinafter described~
(a~ compxession strength ranging from 2 to 4 Kg/cm ;
(b) compression recovery ranging from 80 to 99%;
(c) maximum deceleration ranging from 100 to 50G;
and ;- (d) heat trans~er ratio ranging from 0,031 to 0,020 ' Kcal/m.hour,C, Furthermore, under most favorable conditions~ the product can be provided with compression strength ranging from 3 to
Typical examples of such polymers include poly-styrene, styrene-acrylonitrile copolymer and styrene-malèic anhydride copolymer, so called high-impact polystyrene and high-impact acrylonitrile-butadiene-styrene copolymer (~BS
resin).
It has been confirmed that an extrusion foamed article of thermoplastic resin containing uniform, discrete cells and excelling in compressive strenqth, cushioning property and foaming property is obtained when there is used a styrenic resin containing 3 to 80 weight percent, ;~ preferably 5 to 50 weight percent, of a rubbery substance.
The rubber-reinforced resin used for the present invention is a thermoplastic resin which contains either a diene-type monomer or polymer. Examples o~ the resin are resins such as styrene-butadiene block copolymers (e.g. so called thermoplastic) and styrene-butadiene random copolymers ~- which are obtained by the chemical reaction of a styrene monomer or polymer with a diene-type monomer or polymer, mechanically mixed resins consisting of styrene homopolymers ' bm.
36~
or styrene-based copolymers and diene-type polymers having a rubbery state at normal room temperature. The resins may be used singly or in -the form of mixtures.
As to the melt flow property of the styrenic resin used for the present invention, the MI of said resin is desired to fall in the range of from 0.3 to 30 as deter mined by the method, Condition G, specified by ASTM-D-1238-70.
~ Selection of the blowing agent for use in t~e - 10 present invention is also important. The selection can advantageously be made by taking into account the K~B.
value which will be defined afterward. Generally, there : is used a volatile blowing agen~ having a K.B. value of not more than 25 and a boiling point of not more than 90~C
under normal pressure. The upper limit 25 of the K.B. value is critical because the extrudability aimed at is not ' obtained when a volatile blowing agent having a K.B. value : ,.
exceeding 26 i8 used alone. Concrete examples of such volatile blowing agents are dichlorodifluoromethane (herein ~ 20 after referred to as F-12) (K.B. value 18, boiling point ; -29.8C under normal pressure), monochlorodifluoromethane (hereinafter referred to as F-22) ~K.B. value 25, boiling point ~40.8C), dichlorotetrafluoroethane (hereinafter referred to as F-114) (K.B. value 12, boiling point 3.8C), propane (K.B~ value 23, boiling point -42.1C) and butane (~C.B. value 24, boiling point -0.5C). These volatile blowing agents may be used either singly or in the form of mixtures consisting of two or more members.
In order to ob-tain favorable properties of the extrusion foamed article, it is preferred to use a mixture '. ' `- '-'.
.~ ~
bm.
~ .
: . . . . ~ .... . . . .
,-'' lOq36Z~
which consists of 20 to 90 weight percen-t of at least one member selected from the group of volatile blowing agents possessed of K.B. values of not more than 25 (hereinafter referred to as "group I") and 80 to 10 weight percent of at least one member selected from the group of volatile blowing agents possessed of K~B. values of not less than 26 and boiling points of not more than 90C under normal pressure (hereinafter referred to as "group II"). Although the mixing ratio of these groups I and II is variable with i .-the properties of the particular agents to be actually used, it constitutes an essential requirement for perfect accomplishment of the object of the present invention.: .
Concrete examples of volatile blowing agents of said group II include trichloromonofluoromethane (herein-after referred to as F-ll) (K.B. value 60, boiling point 23.8C under normal pressure), dichloromonofluoromethane ..
(hereinafter referred ~o as F-21) (K~B. value 102, boiling point 8.9~)~ trichlorotrifluoroethane (hereinafter referred : to as F-113) (K.B. value 32, boiling point 47.6C), methyl ch.loride (hereinafter referred to as "MeCQ") (K.B. value 80, boiling point -23.6C), methylene chloride (hereinafter referred to as "MeCQ2") (K.B. value 136, boiling point 40C), pentane (K.B. value 127, boiling point 36.1C) and hexane (K.B. value 30, boiling point 68.~C).
The amount of the blowing agent to be used in the present invention is generally in the range of from 5 to 60 parts by weight and, in case where the effectiveness of the blowing agent demands due attentlon, in the range ; of from 5 to 35 parts by weight based on 100 parts by weight : 30 of the basal resin. It may freely be selected within the ' ' .
- 12 - .
' ' . bm.
:
. .
``` 1~7362Q
~ range so as to satisfy the foaming ahility of the blowing ~ agent and the bulk density which the finally produced foamed article is intended to possess.
If the amount of the volatile blowing agent does not reach the lower limit 5 parts by weigh-t based on 100 --- parts by weight of the basal resin, then the foamed article .. . .
- ~ - consequently obtained fails to acquire uniform cells. If ~ it exceeds the upper limit 60 parts by weight, then the ~- .- ~ --:-~ - cells being formed in the course of continuous foaming are .L0 ruptured, making it impossible to provide continued produc-~ tion of extrusion form having discrete cells of a uniform :.: "' - ' size.
The basal resin of the present invention, as occasion demands, may have incorporated in its component resins or resin blend an effective amount of a stabilizer ;~ serving to repel the action of heat or light or prevent , degradation, an additive useful for enhancing smoothness and impact resistance or a coloriny agent. At the time ~ of extrusion foaming, a suitable amount of a substance ;~ 20 such as, for example, an inorganic carbDnate, organic silicate, inorganic phosphate, metal salt of higher fatty acid, or indigo which is generally used as the nucleic agent, or stabilizing agent may be used additionally for the purpose of adjusting and stabilizing the cell diameter, cell distribution and foaminc~ conditibn. Furthermore, other thermosplastic resins such as polyethylene or rubbery substances can also be used as additives, if necessary.
Also for the purpose of adjusting the cell dia-meter of the foam, an organic nucleic agent ~such as, for example, calcium stearate or barium stearate) and/or , :.; .
bm.
, ~
362~
inorganic n~lcleic agent (such as, for example, talc) may be used in the ordinarily accepted amount.
For practice of the invention, there can be used conventional technique of extrusion foaming which enjoys favorable acceptance for commercial application because of its advantageous productivity. The operational procedure usually comprises the steps of mixing a basal resin and a volatile blowing agent in an extruder at elevated tempera-tures under increased pressure, then cooling the resultant 0 blend for thereby lowering both pressure and temperature to respective levels proper for foaming and subsequently extruding the cooled blend through a die possessed of a desired shape into the atmosphere for thereby causing continuous ~oaming of the extruded blend.
For uniform dispersion of the volatile blowing agent in the basal resin, it is an absolute ~lecessity that said basal resin and volatile blowing agent be blended at elevated temperatures under increased pressure w~thin the extruder. Without uniform dispersion, it is hard to obtain advantageous foaming. At low temperatures, there is a possibility that sufficient blending of the resin and the blo~in~ agent will no longer occur. Furthermore, thexe is , also a possibility that the extrudability of the blend as observed at the time of extrusion foaming will be spoiled.
In addition, the uniformity of distribution of cells in the foamed article will be impaired. Accordingly, the properties of the foamed article will be de~rade~.
Further, at low temperatures, since the viscosity of the .;
. resin is heightened, it becomes necessary to adopt a ~1 30 complicate and expensive extruder of a special structure ;; :
bm.
.
.: ' ' ' -~ ~07~
capable of withstanding the added load and pressure exerted for the actions of extrusion and blending, rendering the commerical production disadvantageous. Under insuf-ficient pressure, there tends to ensue a disadvantage that the blow-ing agent is not uniformly distributed throughout the resin.
In the method of this invention, the temperature and pressure conditions under which the blending is càrried out within the extruder are desired to be such that, in the metering zone or mixing zone of the leading-end portion of ~ 10 the extruder in which the resin and the blowinq a~ent are ; blended more thoroughly than elsewhere, the temperature will fall in the range of from 120 to 300C and the pressure in the range of from 50 to 250 kg~cm , respectively.
` To ensure advantageous foaming, the uniform blend which has been formed under conditions of elevated tempera~
tures and increased pressure must be cooled so that its ; temperature and pressure will both be lowered to levels proper for the desired foaming.
If the blend is extruded in its uncooled state into the atmosphere, there is a fair possibility that the blend will suffer from impaired extrudability which entails disadvantages such as shrinkage of foamed article, loss of surface smoothness and failure to keep a desired shape, for example. There is also a possihility that the individual cells will be heavily ruptured to greatly degrade ~arious properties of the foamed articles. If the blend is suffered to remain under said increased pressure, then it is ex- ;~
tremely difficult to provide desired foaming of the blend and there tends to ensue a disadvantaqe that the individual cells will be heavily ruptured. If the pressure exerted . ' ' bm.
, .: .
'?~
, , . . , :: . . - :. .
~ iO~62~
: , .
on the blend is excessively lowered immediately before the blend is extruded into the atmosphere, there readily ensues a disadvantage that the individual cells will be ruptured to a notable extent. To be more specific, if the extrusion foaming is carried QUt under a pressure lower than the pressure required for liquefying the blowing agent contained ; in the blend, foaming occurs within the foaming unit before the blend is released into the atmosphere, making it difficult to provide the operation and effect of improving the extrudability of the blend and uniformizing the dis-; tribution of discrete cells in the foamed ar-ticle through advantageous utili~tion of the latent heat of evaporation ;~ involved when the blowing agent is vaporized and allowedi . .
~ to fulfill its intended function. Consequently, a dis~
7'-' advantage tends to ensue that the foamed article will have ùnuniform distribution of cells and the individual cells ~; will readily be ruptured.
i j~ ,. . ..
For the purpose of the method of this invention~
the temperature of the blend which is about to be released from the foaming unit into the atmosphere is desired to fall ,;;, .
in the range of from 70 to 110C, preferably from 85 to 100C. Desirably a rotary temperature regulator may be disposed between the extruder and the die so as to enable the temperature and pressure of the blend to be adjusted to proper levels for extrusion foaming.
If, in the method of this invention, there is used a chemical blowing agent (such as, for example, azo-dicarbonamide) which libera-tes upon thermal decomposition a foaming gas such as nitrogen or carbon dioxide which has a very low boiling point and is difficultly miscible with , . .
bm.
. ~
.'~ ' : . ,, ' . ' . . :
3~20 the basal resin, it becomes aifficult to maintain a pressure proper for foaming at the temperature proper for the foamin$
of the basal resin, and the blowing agent itself tends to vaporize within the foaming unit before the blend is r~leased into the atmosphere~ Consequently t there is involved a disadvantage that desirable foaming will no longer be obtained and the distribution of cells in the foamed article will be degraded. There~ore, such a chemical blowing agent is excluded from the scope of the invention.
The method of this invention allows the tempera-ture of the blend to fall in the range of from 70 to 110C
immediately before extrusion foaming. No other method so far developed for the manufacture of a thermoplastic resin foamed article tolerates such a broad temperature range.
This broad temperature range may well be called epochal in the sense that it permits easy commercial production of the , , foam.
For the purpose of the method of this invention, it suffices to have the blend simply released into the atmosphere. h7hen necessary, however, there may be adopted a special device which is capable of keeping the released blend under decreased pressure to the lower limit of 0~2 atm.
According to preferred embodiments, extrusion is performed under conditions such that the extrudate has a thickness ranging from 0.5 to 100 mm, more preferably from 2 to 50 mm and is allowed to an expansion ratîo of from 2 to 50 to produce a foamea article having a thickness of from 1 to 1000 mm, more preferably from 20 to 1000 mm.
The foamed article obtained according to the bm.
.
.
~736~o process of the present invention is found to be ~pecific in having well balanced properties and therefore can be used for a great v~riety of uses, Typically, foa~ed articles having thickness of 2Q mm to 1000 mm, preferably 30 to 500 mm, and bulk density of Z0 to 5~ Kg/m3 produced from a resinous mixture consisting of 40 to 70 wt.~, preferably 45 to 60 wt.%, of an ionomer resin and 60 to 30 wt~, preferably 55 to 40 wt.~ of a styrenic resin containing at least 70 wt.% of styrene or styrene derivative are unexpectedly found to be endowed with all of the following properties: (as measured by the methods as hereinafter described~
(a~ compxession strength ranging from 2 to 4 Kg/cm ;
(b) compression recovery ranging from 80 to 99%;
(c) maximum deceleration ranging from 100 to 50G;
and ;- (d) heat trans~er ratio ranging from 0,031 to 0,020 ' Kcal/m.hour,C, Furthermore, under most favorable conditions~ the product can be provided with compression strength ranging from 3 to
4 Kg/cm , compression recovery ranging from 90 to 99%r maximum deceleration ranging from 90 to 50G and heat transfer ratio ranging from 0,03Q to 0,020, Now, the terms to be used in the specification ' and claims will be defined. The method oE the present invention will be descxibed in further detai:l with reference to said ~referred embodiments and comparative examples, a~ Bulk density (kg/m3) This is expressed by the value resulting from the division of the weight of the extrusion foamed article by the volume thereof. This magnitude is of a nature such that the degree of foaming obtained in the product increases in reverse proportion to said value, bm:p~
:. .
. .
~ 736~0 b) Mean cell diameter (mm) This is expressed by the average value of the dia-meters of all the cells contained within a 100-cm2 cross section of the foamed article.
c) Compression recovery (%) This is expressed by the value calculated from the ., .
~ formula of QfQoX lOO ~ of which the variables Q0 and Q
- are to be found in an experiment comprising the steps . of pressing a foamed article measuring 50 mm x 50 mm x . -10 50 mm for an interual of 0.5 second under the .
. ~ conditions of normal room temperature, 2 m per second of deformation rate and 50 kg/cm of stress until 80%
~ . of the original wall thickness (Q0) of said foam is .; - evenly shrunken, allowing the shrunken foam to stand . -at normal room temperature for a total of 24 hours . and measuring the wall th.ickness (Q) of the foam at "~' the end of said standing.
'. d) Resistance to heat and compression creep (~) .
.~ . This is expressed by the value calculated from the formula- Q0 Ql x 100, of which the variables Q0 and . Ql are to be found respectively in the preceding experiment on the compressive recovery and in a suh- ::
. sequent exper'ment comprising the steps of applying . to the specim~n Eoamed article which has undergone ~.
said preceding experiment a static compressive load of 0.1 kg/cm2 at a controlled temperature of 60C
evenly.in the same direction in which the foamed article was pressed in the preceding experiment, : allowing the foamed article to stand under the applied load for a total of 24 hours and measuring ., . - .
` 19 .: bm.
' . :
~' ,, . . , ~
--` 10~736Z~
the thickness (~1) of the foamed article at the end of the standing.
e) Compression strength (kg/cm ) This is expressed by the value of stress which is exhibited when an extrusion foamed article measuring 50 mm x 50 mm x 50 mm is pressed at a deformation rate of 12.5 mm per minute until 25~ of the original thick-ness is evenly shrunken. Measurements are carried out in the ~ertical, parallel and horizontal directions.
The largest value is determined as the compression strength.
f) Maximum deceleration (G) This is expressed by the value which is obtained by dividing the maximum acceleration registered on the accelerometer by the gravitational acceleration;
the maximum acceleration is to be obtained in an experiment wherein a flat slab having 20 cm and ~! weighing 10 k~ and ~rovided with an accelerometer is dropped onto a rectangular foamed article measuring . 20 14 . 6 cm in area and 3 cm in thickness from the height of an effective length of 60 cm in such way that the slab will exert an even force on the surface of said article in the direction of thickness.
g) Thermal conductivity (Kcal/m.hour.C) This is the value to be obtained by the measure-! ment carried out in accordance with the method specified in ASTM-C-177~
h) Cell porosity (~) A foamed article is kept under reduced pressure of 300 mmHg at normal room temperature for ten minutes.
,.`
, .
:: .
bm.
, ., :, .. , . : ' -; ' - . '.
7362~
The ar~icle, in its unaltered form, is submer~ed in an aqueous 3~ polyethylene glycol (surface active agent) solution and left to stand therein for ten minutes. Then, the article is removed fr~m the solution and wiped to dry the surface and weighed.
(Let Wl stand for the weight thus found.) Let (W0) and (VF) stand for the weight and volume of the article prior to exposure to said reduced pressure.
Then the cell porosity is expressed by the formula, 1 - 0 x 100. This value is of a nature such that F
~ the proportion of dlscrete cells lncreases ln reverse proportion to this value. This means that the suit-ability of the article as a cushioning material or heat-insuIating material increases in reverse proportion to this value.
,.
i) Shrinkage (%) This is expressed by the value to be calculated .~ , from the formula, Bo _ 1 x 100, namely the value corresponding to the difference between the volume of the foamed articles (Bo) measured two minutes after extrusion foaming and the volume (Bl) measured after an interval of three days.
This value represents the de~ree of the dimensional stability of the extrusion foamed article at the time of extrusion foaming. This value is Oe a nature such that the actual dimensions of the extrusion foamed article approach the target dimensions and the work-ability remarkably improves in proportion as the value decreases.
j~ ~ross sectional area (cm2) . , .
. .
. - 21 -,~,; .
bm.
, . ~ .
~,oq36Z~ !
This is expressed by the area of the cross section of the foamed article which is obtained when a foamable resin gel is extrudea through a nozzle, 3.5 mm in diameter, attached to the leading end of an extruder 30 mm in screw diameter with an extruding capacity of 3.8 kg/hour into a zone of atmospheric pressure. Said foamable resin ~el is prepared by mixing 100 parts by weight of basal polymer with 21 parts by weight of a blowing agent with a view to uniformizing the bulk density to the fullest possible extent.
k) Kauri-Butanol (K.B. ) value This is measured hy the method of ASTM-D-1133-61.
. -The ionomer resins used in the preferred embodiments of this invention and the comparative examples were invariably trial products (A through L) by Asahi-Dow Limited. In each product, A through J, the acid component is methacrylic acid. The products K and contain methacrylic acid as acid component and methyl.
; methacrylate as ester component. The typical numerical values of their properties are shown in Table 1.
.~ '. .
, ' ' , "' '` ' .~:
: ~
;.
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bm.
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10~3 -I ~ ----~ ----~ tn o ~i ~ co ~' ~
.... ___ I _ __ _ I~ ..
K r` ~ ) o ,~ : . .
o o ~ r) . ~.
_ .. __ ~ ..... ..... _ _ .. _. _. _ __ . : .oo o ~ : ' 7 ~ ~ Ul o o '., In O O O ~1 __'1 .. , ~.
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3~2~
Example 1 and Comparative Example 1:
Six types of ionomer resins A, E, G, H, I and J
and three types of polystyrene resins [Styron (trade mark) 680 (MI 8.0), a product by Asahi~Dow Limited], [Styron (trade mark) 666 (MI 7.0), a product by same company] and [Styron (trade mark) 679 (MI 25.5j, a product by same company] were mixed in the combinations and at -the percent compositions indicated in Table 2 to prepare basal resins.
From each of the basal resins was prepared a mixed resin by dry blending 100 parts by weight of the basal resin with O.S part by weight each of talc and zinc stearate.
The mixed resin was fed through a resin inlet into an extruder (30 mm in screw diameter) having the first zone maintained at 125C and the second and third zones each at , 190C, causing the resin to be melted and kneaded. Through a blowing agent inlet disposed in the neighborhood of the , starting point of the third zone of said extruder, a blowing agent prepared separately (by mixing 80 parts by weight of dichlorodifluoromethane with 20 parts by weight of methylene chloride) was introduced under increased pressure at a rate .,i . . ~
; of 21 parts by weight of said blowing agent per 100 parts by weight of the basal resin, allowing the blowing àgent to .
be dispersed in said molten resin. The pressure under which the introduction of blowing agent was effected in this case ~.
(corresponding to the back pressure of the extruder) was found to fall in the range of from 105 to 115 kg/cm . The ` molten resin flowed through the cooling and kneading zones and consequently had its temperature adjusted to about 100C.
Then, it was extruded through a nozzle 3.5 mm in diameter ~ 30 into an atmosphere zone at an extrusion capacity of 3.8 : - 2~ -bm.
j`, ' ' .
. " .
" ~0~362~
kg/hour to produce an e~trusion foamed article.
The article thus produced was examined by way of rating the extrudability of the corresponding basal resins.
The results of the rating were as shown in Table 2. In Table 2, the basal resins (composed of ionomer and poly-styrene resins) having polystyrene resin contents in the range of from 10 to 70 percents are indicated as belonging to Example 1 and those having polystyrene resin contents of
:. .
. .
~ 736~0 b) Mean cell diameter (mm) This is expressed by the average value of the dia-meters of all the cells contained within a 100-cm2 cross section of the foamed article.
c) Compression recovery (%) This is expressed by the value calculated from the ., .
~ formula of QfQoX lOO ~ of which the variables Q0 and Q
- are to be found in an experiment comprising the steps . of pressing a foamed article measuring 50 mm x 50 mm x . -10 50 mm for an interual of 0.5 second under the .
. ~ conditions of normal room temperature, 2 m per second of deformation rate and 50 kg/cm of stress until 80%
~ . of the original wall thickness (Q0) of said foam is .; - evenly shrunken, allowing the shrunken foam to stand . -at normal room temperature for a total of 24 hours . and measuring the wall th.ickness (Q) of the foam at "~' the end of said standing.
'. d) Resistance to heat and compression creep (~) .
.~ . This is expressed by the value calculated from the formula- Q0 Ql x 100, of which the variables Q0 and . Ql are to be found respectively in the preceding experiment on the compressive recovery and in a suh- ::
. sequent exper'ment comprising the steps of applying . to the specim~n Eoamed article which has undergone ~.
said preceding experiment a static compressive load of 0.1 kg/cm2 at a controlled temperature of 60C
evenly.in the same direction in which the foamed article was pressed in the preceding experiment, : allowing the foamed article to stand under the applied load for a total of 24 hours and measuring ., . - .
` 19 .: bm.
' . :
~' ,, . . , ~
--` 10~736Z~
the thickness (~1) of the foamed article at the end of the standing.
e) Compression strength (kg/cm ) This is expressed by the value of stress which is exhibited when an extrusion foamed article measuring 50 mm x 50 mm x 50 mm is pressed at a deformation rate of 12.5 mm per minute until 25~ of the original thick-ness is evenly shrunken. Measurements are carried out in the ~ertical, parallel and horizontal directions.
The largest value is determined as the compression strength.
f) Maximum deceleration (G) This is expressed by the value which is obtained by dividing the maximum acceleration registered on the accelerometer by the gravitational acceleration;
the maximum acceleration is to be obtained in an experiment wherein a flat slab having 20 cm and ~! weighing 10 k~ and ~rovided with an accelerometer is dropped onto a rectangular foamed article measuring . 20 14 . 6 cm in area and 3 cm in thickness from the height of an effective length of 60 cm in such way that the slab will exert an even force on the surface of said article in the direction of thickness.
g) Thermal conductivity (Kcal/m.hour.C) This is the value to be obtained by the measure-! ment carried out in accordance with the method specified in ASTM-C-177~
h) Cell porosity (~) A foamed article is kept under reduced pressure of 300 mmHg at normal room temperature for ten minutes.
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7362~
The ar~icle, in its unaltered form, is submer~ed in an aqueous 3~ polyethylene glycol (surface active agent) solution and left to stand therein for ten minutes. Then, the article is removed fr~m the solution and wiped to dry the surface and weighed.
(Let Wl stand for the weight thus found.) Let (W0) and (VF) stand for the weight and volume of the article prior to exposure to said reduced pressure.
Then the cell porosity is expressed by the formula, 1 - 0 x 100. This value is of a nature such that F
~ the proportion of dlscrete cells lncreases ln reverse proportion to this value. This means that the suit-ability of the article as a cushioning material or heat-insuIating material increases in reverse proportion to this value.
,.
i) Shrinkage (%) This is expressed by the value to be calculated .~ , from the formula, Bo _ 1 x 100, namely the value corresponding to the difference between the volume of the foamed articles (Bo) measured two minutes after extrusion foaming and the volume (Bl) measured after an interval of three days.
This value represents the de~ree of the dimensional stability of the extrusion foamed article at the time of extrusion foaming. This value is Oe a nature such that the actual dimensions of the extrusion foamed article approach the target dimensions and the work-ability remarkably improves in proportion as the value decreases.
j~ ~ross sectional area (cm2) . , .
. .
. - 21 -,~,; .
bm.
, . ~ .
~,oq36Z~ !
This is expressed by the area of the cross section of the foamed article which is obtained when a foamable resin gel is extrudea through a nozzle, 3.5 mm in diameter, attached to the leading end of an extruder 30 mm in screw diameter with an extruding capacity of 3.8 kg/hour into a zone of atmospheric pressure. Said foamable resin ~el is prepared by mixing 100 parts by weight of basal polymer with 21 parts by weight of a blowing agent with a view to uniformizing the bulk density to the fullest possible extent.
k) Kauri-Butanol (K.B. ) value This is measured hy the method of ASTM-D-1133-61.
. -The ionomer resins used in the preferred embodiments of this invention and the comparative examples were invariably trial products (A through L) by Asahi-Dow Limited. In each product, A through J, the acid component is methacrylic acid. The products K and contain methacrylic acid as acid component and methyl.
; methacrylate as ester component. The typical numerical values of their properties are shown in Table 1.
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3~2~
Example 1 and Comparative Example 1:
Six types of ionomer resins A, E, G, H, I and J
and three types of polystyrene resins [Styron (trade mark) 680 (MI 8.0), a product by Asahi~Dow Limited], [Styron (trade mark) 666 (MI 7.0), a product by same company] and [Styron (trade mark) 679 (MI 25.5j, a product by same company] were mixed in the combinations and at -the percent compositions indicated in Table 2 to prepare basal resins.
From each of the basal resins was prepared a mixed resin by dry blending 100 parts by weight of the basal resin with O.S part by weight each of talc and zinc stearate.
The mixed resin was fed through a resin inlet into an extruder (30 mm in screw diameter) having the first zone maintained at 125C and the second and third zones each at , 190C, causing the resin to be melted and kneaded. Through a blowing agent inlet disposed in the neighborhood of the , starting point of the third zone of said extruder, a blowing agent prepared separately (by mixing 80 parts by weight of dichlorodifluoromethane with 20 parts by weight of methylene chloride) was introduced under increased pressure at a rate .,i . . ~
; of 21 parts by weight of said blowing agent per 100 parts by weight of the basal resin, allowing the blowing àgent to .
be dispersed in said molten resin. The pressure under which the introduction of blowing agent was effected in this case ~.
(corresponding to the back pressure of the extruder) was found to fall in the range of from 105 to 115 kg/cm . The ` molten resin flowed through the cooling and kneading zones and consequently had its temperature adjusted to about 100C.
Then, it was extruded through a nozzle 3.5 mm in diameter ~ 30 into an atmosphere zone at an extrusion capacity of 3.8 : - 2~ -bm.
j`, ' ' .
. " .
" ~0~362~
kg/hour to produce an e~trusion foamed article.
The article thus produced was examined by way of rating the extrudability of the corresponding basal resins.
The results of the rating were as shown in Table 2. In Table 2, the basal resins (composed of ionomer and poly-styrene resins) having polystyrene resin contents in the range of from 10 to 70 percents are indicated as belonging to Example 1 and those having polystyrene resin contents of
5 and 95 percents as belonging to Comparative Example 1 respectively.
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:
1~362~
Example 2 and Comparative Example 2:
Basal resins were prepared by following the :~
~ procedure of Example 1, except the ionomer resin E and a styrene-butadiene copolymer (butadiene content 8 weight .
percent, MFI 7.0 g/10 minutes) were used in the amounts inaicated in Table 3. :
~: Table 3 ~:~
~ . _ ~ . .
Amount Item of Bulk Mban Shrink- Cross :-10 ~ \ styrene den- cell age sec-. ~ \ buta- sity poro- (%) tiona~ Foaming \ diene (kcJ/ sity area :: sifi \ polymer m3) (~m) (cm2) cation .\ .(wt.%).
_ ~ ~ ., _ .
. 15 31.0 0.5 1.70 8.2 Gcod surface smoothness and ; Exa~ple uni~orm foamin~ . .
. 2 40 - 34.. 2 0.6 0.30 11.9 ll p. ~0 35.4 0.8 1.~0 ~0.1 ll ~
......... . .. . . .... . . .
'.' _ ., _ : :
5 . 32.1 1.1 3.10 5.2 Slightly poor -~ Co~para- surfaoe smooth tive ness and un-Examp~e . . unifonm foamin : ..
. _ 95 36.0 ~.2 e.lo 5.l i _ " _ ..::, _ .
Example 3 and Comparative Example 3:
.The procedure of Example 1 was repeated, . except that a mixed resin consisting of 50 weight percent ....
of ionomer resin E and 50 weight percent of polystyrene resin ~Styron (trade mark) 680] was used as the basa]. resin and dichlorodifluoromethane (F-12) alone, propane alonè, a . 50/50 (by weight ratio; the same applicable hereinafter) . 30 mixture of F-12/methyl chloride (MeCQ~, a 50/50 mixture of .,' .
_ ~7 _ .
bm.
73~2~ :
propane/methyl chloride and a 75/25 mixture of F-l~/methylene chloride (MeCQ2) (belonging to Example 3), methylene chloride alone, -trichloromonofluoromethane (F-ll) alone and pentane alone (belonging to Comparative Example 3) were used as the blowing agent to be introduced into the basal resin. The extrusion foamed articles thus obtained were examined to rate the extrudability of the corresponding basal resins at the time of extrusion. The results of the rating were as shown ; in Table 4.
The pressure under which the blowing agent was introduced in this case invariably fell in the range of from 105 to 115 kg/cm2.
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Example 4 and Comparative ExampIe 4:
Extrusion foamed articles were produced by follow-ing the procedure of Example 3 and Comparati~e Example 3, except 80/20, 75/25, 50/50 and 40/60 mixtures respectively of F-12/MeCQ2, 80/20 and 60/40 mixtures respectively of propane/MeCQ, 50/50 mixture of propane/pentane and an 80/20 mixture of F-12/hexane (belonging to Example 4) were used each as the blowing agent. They were examined by way of rating the e,xtrudability of the corresponding basal ' ' resins and were tested for properties. The results were , as shown in Table 5. The pressure at which the blowing agent was introduced invari,ably fell in the neighborhood of 110 kg/cm2.
For referential purposes, molten resins to be extruded were prepared in the percent composition indi-cated herein below and they were extruded under the optimum conditions to produce foamed axticles. I`he ~, articles were similarly examined and tested. The results ''~ were as shown in Table 5.
The principal conditions involved in the Compara-, ,tive Example 4 and particular notes are shown below. In each case, the extrusion temperature is kept at about 100C
~; (Sample 1) Resin used: Ionomer resin lSamPle No. C (MI0.56)]
alone Blowing agent: F-12 alone , Specific conditions:
(1) When the blowing agent was used at a ratio of , 21 parts by weight per 100 parts by weight of ,, 30 the resin, the foaming proceeded to the .- .
'~ - 30 - -bm.
.
.. , . ' ' extent of bringing about abnormal expansion.
Thus, the amount of the blowing agent was reduced to 11 parts by weight.
(2) When an attempt was made to fix the extrusion volume at 2 kg/hour (target 3.8 kg/hour), there appeared indications of a possibility that the pressure of introduction (corresponding to hack pressure) would exceed the critical value of press~re resistance. Thus, the extrusion was performed at a decreased extrusion volume of 1.8 kg/hour. In this case, the pressure of introduction rose to an abnormally high level ; of 210 kg/cm2.
(Sample 2) i~ Resin used: Polystyrene [Styron (trade maxk) 680, a ; product by Asahi-Dow Limited] alone Blowing agent: A 40/60 mixture of F-12/MeC~
Specific conditions:
(1) When the blowing agent was used at a ratio ; 20 of 21 parts by weight per 100 parts by weight : . .
of the resin, the foaming proceeded to -the extent of bringing about abnormal expansion.
i Thus, the amount of the blowing agent was decreased to 16 parts by weight. In this case, the pressure for introduction of the blowing agent was 120 kg/cm2.
~Sample 3) Resin used: Low-density ~non-cross-linked) poly `3 ethylene resin [M-2125 ~trade mark) ~ 30 produced by Asahi-Dow Limited, MI 2.5, .,,,. .
~',~ ' ' bm.
',' ' . ' ' 11)~3~;2~
.
density 0.921 g/cc] alone slowing agent: Dichlorotetrafluoroethane (F-114 alone Specific conditions: :
(1) When the blowlng agent was used at a ratio :~
of 21 parts by weight per 100 parts by weight ...
of the resin, the expansion ratio was not . . sufficiently high. Thus, the amount of the ~ ;
blowing agent was increased to 24 parts by weight. The pressure for introduction of the ; blowing agent in this case was 110 kg/cm2.
~Sample 4) Resin used: A mixea resin consisting of 65 parts by weight of low-density polyethylene ~ resin ~Yukalon (trade mark) HE-60 made :; by Mitsubishi Petrochemical Co.] and , .
35 parts by weight of polystyrene resin ! . [Styron (trade mark) 679 made by Asahi-Dow Limited~
Blowing agent: F-ll alone , Specific conditions:
100 parts (by welght) of the above resin, 0.5 . part of talcum, 0.005 part of polybutene and .~
24 parts of freon were introduced at 210C
into an extruder. The pressure for intro-~ duction of the blowing agent in this case.
`~ was 115 kg/cm2.
.. (Samples 5, 6 and 7) The procedure for Sample 4 was repeated, except a 50/50 (by weight ratio) mixture of F-ll and butane, a . 50/50 (by weight ratio) mixture of F-ll and F-12 and .. . .
. . .
bm.
.
736Z~
a 50/50 (by weight ratio) mixture of F-11 and propane were usea each as the blowing agent at a ratio a 25 parts by weight based on 100 parts by weight of the basal resin.
In this case, the pressure of introduction was 105 to 110 kg/cm 2 . ' '~' ,' . . .
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As is clear from the comparison of Example 4 and Samples 4, 5, 6 and 7 o~ Comparative Example 4, the foamed articles obtained in Sa~ples 4, 5, 6 and 7 by extruding the corresponding melts into the atmosphere at 23C ha~ small cross sectional areas and large percents of shrinkage as compared with those obtained in Example 4. These articles had too inferior properties to be used effectively as the cushioning material. These degraded properties may possibly be ascribed to the shrinkage which the articles underwent and to opened cells. These foamed articles showed very high degrees of cell porosity possibly because the basal resins contained no ionomer resin and, ther~fore, the compatibility between polyethylene and polystyrene was not sufficiently high desp~te the use of suitable blowing ~ agents. This trend toward degradation of properties became `; conspicuous as the thickness of extrusion foamed article exceeded 10 mm. The state of distribution af cells in the product of Example 4 and its enlarged view are shown in Figs. 1 and 2, respectively. For comparative purpose, the state of cells in the product of Sample 5, 6, or 7 and its enlarged view are shown in Figs. 3 and 4, respectively.
Example 5:
Foamed articles were produced by repeating the procedure of Example 1, except basal resins were prepared by mixing a total of 10 types of ionomer resins, A through J, each with Styron (trade mark) 680 as the styrene resin, at a ratio of 50/50 and an ~0/20 mixture of F-12/MeCQ was used as the blowing agent. The extrusion foamed articles were examined by way of rating the extrudability of the corresponding basal resins and were tested for properties.
:
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Example 6:
A basal resin was prepared by mixing 50 weight percent of ionomer resin (Sample No. C, MI 0.56) and 50 weight percent of an impact-resistant polystyrene resin containing 3 weight percent of polybutadiene (manufactured product by Asahi-Dow Limited). A mixture consisting of lO0 parts by weight of said basal resin and 0.5 part by weight of talc and 0.4 part by weight of barium steara~e was fed to an extruder having 30 mm in screw diameter and having the first zone kept at 120C, the second zone at 210~C and the third zone at 240C. Through an inlet disposed in the middle of the third zone of said extruder, a mixed volatile blowing agent consisting of 30 wei~ht percent of dichlorodifluoromethane and 70 weight percent of dichloromonofluoromethane was introduced under increased pressure at a ratio of 31 parts by weight per lO0 parts by weight of said basal resin to be blended ! therewith. The blend was extruded through a die (3 mm in diameter) attached to the forward tip of the temperature adjusting member at a resin temperature of 105C into a ; low-pressure zone at the highest extruding capacity 3.3 kg/hour of the extruder, to undergo extrusion foaming.
At this time, the pressure for introduction of the blowin~
agent was 170 kg/cm~ and the resin pressure immediately in ront o the die was 35 kg/cm2.
The bar-shaped foamed article thus obtained had a bulk density of 25 kg/m3, contained uniform, discrete cells and enjoyed good surface smoothness. The ratio of voluminal decrease of the foamed article at the end of 48 ; 30 hours' standing from the time of foaming was 2~, ' ' : . .
bm.
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an exceptionally small value. The compressive strength was 1.8 kg/cm2 and the maximurn deceleration was 65 G.
Example 7:
The procedure of Example 6 was repeated, except a styrenebutadiene block copolymer containing 70 weight percent of butadiene was used in place of the impact-resistant polystyrene containing polybutadiene. In this case, the pressure for introduction of the blowing agent was 150 kg/cm2 and the pressure of the resin immediately in front of the die was 31 kg/cm2.
The bar-like foame~ article thus produced showed a bulk density of 3~ ky/m3, contained uniform, discrete cells and had slightly coarse surface. The ratio of voluminal decrease of the foamed article at the end of 48 hours' standlng from the time of foaming was 5%. The article showed a compressive strength of 1.2 kg/cm2 and a maximum deceleration of 51 G, indicating that it excelled in cushioning property.
Examples 8 - 14 and comparative-Examples 5 - 6:
As the ionomer resin, there were used Sample No.
C (MI 0.56) and Sample No. D (MI 1.2) and Sample No. K
r (Ca as metal, MI 0.7, S - 75%, N = 50~) and Sample No. L
,~ .
(Na as metal, MI 1.5, S = 58%, N = 45~). As the rubbery substance-containing thermoplastic resin, there were used ` a polystyrene resin containing 3 weight percent of poly-:, .
,~ butadiene (hereinafter abbreviated as "X"), a polystyrene .~ .
resin containing 18 weight percent of polybutadiene , (hereinafter abbreviated as "Y") and a mixed resin consist-ing of 20 parts by weight of polystyrene resin, Styron ,~ 30 (trade mark) 680, produced by Asahi-Dow Limited and 80 i~:
:,.
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parts by weight o~ polybutadiene rubber, Diene (trade mark) produced by Asahi Chemical Industry Co., Ltd. (hereinafter abbreviated as "Z"). They were mixed at the ratios indi-cated in Table 7 to prepare basal resins. Then, the procedure of Example 6 was repeated, except the afore-mentioned basal resins were used and the blowing agents prepared by mixing F~12,'F-21, F-11, F-114 and ~eCQ2 at the rat,ios indicated in Table 7 were used as the volatile blowing agent.
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The present invention permits an extrusion foam-ing of thermoplastic synthetic resin to be accomplished with enhanced efficiency. For example, this invention is effective in preventing the resin from being expanded or shrunken at the t.ime of extrusion, improving the extxusion foamed article in terms of cross section and keeping the extrusion back pressure from abnormally increasing and, consequently, brings about an effect of improving the ec.on~my of the extruding and foaming steps. In addition, this invention p.ermi.ts economically advantageous production of a novel resin foamed article capable of satisfying the various properties such as compression strength and recovery, cushioning property, and thermal insulatin~
property all at once.
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Example 2 and Comparative Example 2:
Basal resins were prepared by following the :~
~ procedure of Example 1, except the ionomer resin E and a styrene-butadiene copolymer (butadiene content 8 weight .
percent, MFI 7.0 g/10 minutes) were used in the amounts inaicated in Table 3. :
~: Table 3 ~:~
~ . _ ~ . .
Amount Item of Bulk Mban Shrink- Cross :-10 ~ \ styrene den- cell age sec-. ~ \ buta- sity poro- (%) tiona~ Foaming \ diene (kcJ/ sity area :: sifi \ polymer m3) (~m) (cm2) cation .\ .(wt.%).
_ ~ ~ ., _ .
. 15 31.0 0.5 1.70 8.2 Gcod surface smoothness and ; Exa~ple uni~orm foamin~ . .
. 2 40 - 34.. 2 0.6 0.30 11.9 ll p. ~0 35.4 0.8 1.~0 ~0.1 ll ~
......... . .. . . .... . . .
'.' _ ., _ : :
5 . 32.1 1.1 3.10 5.2 Slightly poor -~ Co~para- surfaoe smooth tive ness and un-Examp~e . . unifonm foamin : ..
. _ 95 36.0 ~.2 e.lo 5.l i _ " _ ..::, _ .
Example 3 and Comparative Example 3:
.The procedure of Example 1 was repeated, . except that a mixed resin consisting of 50 weight percent ....
of ionomer resin E and 50 weight percent of polystyrene resin ~Styron (trade mark) 680] was used as the basa]. resin and dichlorodifluoromethane (F-12) alone, propane alonè, a . 50/50 (by weight ratio; the same applicable hereinafter) . 30 mixture of F-12/methyl chloride (MeCQ~, a 50/50 mixture of .,' .
_ ~7 _ .
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73~2~ :
propane/methyl chloride and a 75/25 mixture of F-l~/methylene chloride (MeCQ2) (belonging to Example 3), methylene chloride alone, -trichloromonofluoromethane (F-ll) alone and pentane alone (belonging to Comparative Example 3) were used as the blowing agent to be introduced into the basal resin. The extrusion foamed articles thus obtained were examined to rate the extrudability of the corresponding basal resins at the time of extrusion. The results of the rating were as shown ; in Table 4.
The pressure under which the blowing agent was introduced in this case invariably fell in the range of from 105 to 115 kg/cm2.
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Example 4 and Comparative ExampIe 4:
Extrusion foamed articles were produced by follow-ing the procedure of Example 3 and Comparati~e Example 3, except 80/20, 75/25, 50/50 and 40/60 mixtures respectively of F-12/MeCQ2, 80/20 and 60/40 mixtures respectively of propane/MeCQ, 50/50 mixture of propane/pentane and an 80/20 mixture of F-12/hexane (belonging to Example 4) were used each as the blowing agent. They were examined by way of rating the e,xtrudability of the corresponding basal ' ' resins and were tested for properties. The results were , as shown in Table 5. The pressure at which the blowing agent was introduced invari,ably fell in the neighborhood of 110 kg/cm2.
For referential purposes, molten resins to be extruded were prepared in the percent composition indi-cated herein below and they were extruded under the optimum conditions to produce foamed axticles. I`he ~, articles were similarly examined and tested. The results ''~ were as shown in Table 5.
The principal conditions involved in the Compara-, ,tive Example 4 and particular notes are shown below. In each case, the extrusion temperature is kept at about 100C
~; (Sample 1) Resin used: Ionomer resin lSamPle No. C (MI0.56)]
alone Blowing agent: F-12 alone , Specific conditions:
(1) When the blowing agent was used at a ratio of , 21 parts by weight per 100 parts by weight of ,, 30 the resin, the foaming proceeded to the .- .
'~ - 30 - -bm.
.
.. , . ' ' extent of bringing about abnormal expansion.
Thus, the amount of the blowing agent was reduced to 11 parts by weight.
(2) When an attempt was made to fix the extrusion volume at 2 kg/hour (target 3.8 kg/hour), there appeared indications of a possibility that the pressure of introduction (corresponding to hack pressure) would exceed the critical value of press~re resistance. Thus, the extrusion was performed at a decreased extrusion volume of 1.8 kg/hour. In this case, the pressure of introduction rose to an abnormally high level ; of 210 kg/cm2.
(Sample 2) i~ Resin used: Polystyrene [Styron (trade maxk) 680, a ; product by Asahi-Dow Limited] alone Blowing agent: A 40/60 mixture of F-12/MeC~
Specific conditions:
(1) When the blowing agent was used at a ratio ; 20 of 21 parts by weight per 100 parts by weight : . .
of the resin, the foaming proceeded to -the extent of bringing about abnormal expansion.
i Thus, the amount of the blowing agent was decreased to 16 parts by weight. In this case, the pressure for introduction of the blowing agent was 120 kg/cm2.
~Sample 3) Resin used: Low-density ~non-cross-linked) poly `3 ethylene resin [M-2125 ~trade mark) ~ 30 produced by Asahi-Dow Limited, MI 2.5, .,,,. .
~',~ ' ' bm.
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.
density 0.921 g/cc] alone slowing agent: Dichlorotetrafluoroethane (F-114 alone Specific conditions: :
(1) When the blowlng agent was used at a ratio :~
of 21 parts by weight per 100 parts by weight ...
of the resin, the expansion ratio was not . . sufficiently high. Thus, the amount of the ~ ;
blowing agent was increased to 24 parts by weight. The pressure for introduction of the ; blowing agent in this case was 110 kg/cm2.
~Sample 4) Resin used: A mixea resin consisting of 65 parts by weight of low-density polyethylene ~ resin ~Yukalon (trade mark) HE-60 made :; by Mitsubishi Petrochemical Co.] and , .
35 parts by weight of polystyrene resin ! . [Styron (trade mark) 679 made by Asahi-Dow Limited~
Blowing agent: F-ll alone , Specific conditions:
100 parts (by welght) of the above resin, 0.5 . part of talcum, 0.005 part of polybutene and .~
24 parts of freon were introduced at 210C
into an extruder. The pressure for intro-~ duction of the blowing agent in this case.
`~ was 115 kg/cm2.
.. (Samples 5, 6 and 7) The procedure for Sample 4 was repeated, except a 50/50 (by weight ratio) mixture of F-ll and butane, a . 50/50 (by weight ratio) mixture of F-ll and F-12 and .. . .
. . .
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.
736Z~
a 50/50 (by weight ratio) mixture of F-11 and propane were usea each as the blowing agent at a ratio a 25 parts by weight based on 100 parts by weight of the basal resin.
In this case, the pressure of introduction was 105 to 110 kg/cm 2 . ' '~' ,' . . .
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As is clear from the comparison of Example 4 and Samples 4, 5, 6 and 7 o~ Comparative Example 4, the foamed articles obtained in Sa~ples 4, 5, 6 and 7 by extruding the corresponding melts into the atmosphere at 23C ha~ small cross sectional areas and large percents of shrinkage as compared with those obtained in Example 4. These articles had too inferior properties to be used effectively as the cushioning material. These degraded properties may possibly be ascribed to the shrinkage which the articles underwent and to opened cells. These foamed articles showed very high degrees of cell porosity possibly because the basal resins contained no ionomer resin and, ther~fore, the compatibility between polyethylene and polystyrene was not sufficiently high desp~te the use of suitable blowing ~ agents. This trend toward degradation of properties became `; conspicuous as the thickness of extrusion foamed article exceeded 10 mm. The state of distribution af cells in the product of Example 4 and its enlarged view are shown in Figs. 1 and 2, respectively. For comparative purpose, the state of cells in the product of Sample 5, 6, or 7 and its enlarged view are shown in Figs. 3 and 4, respectively.
Example 5:
Foamed articles were produced by repeating the procedure of Example 1, except basal resins were prepared by mixing a total of 10 types of ionomer resins, A through J, each with Styron (trade mark) 680 as the styrene resin, at a ratio of 50/50 and an ~0/20 mixture of F-12/MeCQ was used as the blowing agent. The extrusion foamed articles were examined by way of rating the extrudability of the corresponding basal resins and were tested for properties.
:
., bm.
~",1 , . . ..
36Z~ -'l'he results were as shown in 'rable 6. For referential purposes, the results obtained with respect to aforesaid Samples 1 through 3 of Compartive Example 4 are also given in the same table.
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., _ __ _ _ . ~
o o ~ : .
. . .
o o o . ~ . _ o o . .
.;, ~ o r~ ~ ., o o o ., .. ~ o o o o _ __ __ r~ r ~D . ~1 ' ':
____ ,. .
' ~1 1` u~ ~
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., ~ Lt~ ~ ~
`,. E~
,., Ln O 1`
. ~ a~
. ~ ~ cn . .
~. o o q~
,. ~
. ~ Ul 'J
~ ~ oo `,~ o o o .. _ ~.,. ~
,.i ~r o co ~., ~ ~ ~
,.1 .
I I ~
,~ ~1 .
, h a) :~
O ~ h I u ;~ ~ 3 1 ;., O 0~) 0 Q) 0~
~ H L4 U~ ~ ~ ~ Q) _ . ..
,i I ~ ~ ~ ~
.,. , I ~ I
~I Q
.; O (~ ~1 X E~
U Q,~ W (~ n. ~ Q. .c~
i.
. -- 39 --:. .
~ bm.
,~ .,. ,... . . ., .. . , , . :. : . .
- . :,.. , . . . .: . .: :. . :
. . . . . . .. . . .
1~36Z~
Example 6:
A basal resin was prepared by mixing 50 weight percent of ionomer resin (Sample No. C, MI 0.56) and 50 weight percent of an impact-resistant polystyrene resin containing 3 weight percent of polybutadiene (manufactured product by Asahi-Dow Limited). A mixture consisting of lO0 parts by weight of said basal resin and 0.5 part by weight of talc and 0.4 part by weight of barium steara~e was fed to an extruder having 30 mm in screw diameter and having the first zone kept at 120C, the second zone at 210~C and the third zone at 240C. Through an inlet disposed in the middle of the third zone of said extruder, a mixed volatile blowing agent consisting of 30 wei~ht percent of dichlorodifluoromethane and 70 weight percent of dichloromonofluoromethane was introduced under increased pressure at a ratio of 31 parts by weight per lO0 parts by weight of said basal resin to be blended ! therewith. The blend was extruded through a die (3 mm in diameter) attached to the forward tip of the temperature adjusting member at a resin temperature of 105C into a ; low-pressure zone at the highest extruding capacity 3.3 kg/hour of the extruder, to undergo extrusion foaming.
At this time, the pressure for introduction of the blowin~
agent was 170 kg/cm~ and the resin pressure immediately in ront o the die was 35 kg/cm2.
The bar-shaped foamed article thus obtained had a bulk density of 25 kg/m3, contained uniform, discrete cells and enjoyed good surface smoothness. The ratio of voluminal decrease of the foamed article at the end of 48 ; 30 hours' standing from the time of foaming was 2~, ' ' : . .
bm.
, .
.. . .... . ... .. .
. ~ . . . .. . . .. .. ..
:
~~ iO73~2~
an exceptionally small value. The compressive strength was 1.8 kg/cm2 and the maximurn deceleration was 65 G.
Example 7:
The procedure of Example 6 was repeated, except a styrenebutadiene block copolymer containing 70 weight percent of butadiene was used in place of the impact-resistant polystyrene containing polybutadiene. In this case, the pressure for introduction of the blowing agent was 150 kg/cm2 and the pressure of the resin immediately in front of the die was 31 kg/cm2.
The bar-like foame~ article thus produced showed a bulk density of 3~ ky/m3, contained uniform, discrete cells and had slightly coarse surface. The ratio of voluminal decrease of the foamed article at the end of 48 hours' standlng from the time of foaming was 5%. The article showed a compressive strength of 1.2 kg/cm2 and a maximum deceleration of 51 G, indicating that it excelled in cushioning property.
Examples 8 - 14 and comparative-Examples 5 - 6:
As the ionomer resin, there were used Sample No.
C (MI 0.56) and Sample No. D (MI 1.2) and Sample No. K
r (Ca as metal, MI 0.7, S - 75%, N = 50~) and Sample No. L
,~ .
(Na as metal, MI 1.5, S = 58%, N = 45~). As the rubbery substance-containing thermoplastic resin, there were used ` a polystyrene resin containing 3 weight percent of poly-:, .
,~ butadiene (hereinafter abbreviated as "X"), a polystyrene .~ .
resin containing 18 weight percent of polybutadiene , (hereinafter abbreviated as "Y") and a mixed resin consist-ing of 20 parts by weight of polystyrene resin, Styron ,~ 30 (trade mark) 680, produced by Asahi-Dow Limited and 80 i~:
:,.
, .
brn.
: .'`1 - , . ~ : , 36~
parts by weight o~ polybutadiene rubber, Diene (trade mark) produced by Asahi Chemical Industry Co., Ltd. (hereinafter abbreviated as "Z"). They were mixed at the ratios indi-cated in Table 7 to prepare basal resins. Then, the procedure of Example 6 was repeated, except the afore-mentioned basal resins were used and the blowing agents prepared by mixing F~12,'F-21, F-11, F-114 and ~eCQ2 at the rat,ios indicated in Table 7 were used as the volatile blowing agent.
- 42 - :
bm.
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362~
The present invention permits an extrusion foam-ing of thermoplastic synthetic resin to be accomplished with enhanced efficiency. For example, this invention is effective in preventing the resin from being expanded or shrunken at the t.ime of extrusion, improving the extxusion foamed article in terms of cross section and keeping the extrusion back pressure from abnormally increasing and, consequently, brings about an effect of improving the ec.on~my of the extruding and foaming steps. In addition, this invention p.ermi.ts economically advantageous production of a novel resin foamed article capable of satisfying the various properties such as compression strength and recovery, cushioning property, and thermal insulatin~
property all at once.
~:
. ' . .
' ' :'. ' . .
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:' ~
.. . .
.
' ; - 45 -: bm.
- : : :' ' ' :
Claims (14)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for producing a foamed article which comprises blending 10 to 90% by weight of an ionomer resin having a melt index from 0.1 to 50 g/10 min. and 90 to 10%
by weight of a styrenic synthetic resin, and mixing 100 parts by weight of the resulting blend in the molten state with 5 to 60 parts by weight of a volatile blowing agent, having a Kauri-butanol value up to 25, in an extruder at high temper-ature and pressure, and extruding the resulting blended mixture into a zone kept under a pressure which is not higher than atmospheric pressure, thereby allowing the extrudate to expand.
by weight of a styrenic synthetic resin, and mixing 100 parts by weight of the resulting blend in the molten state with 5 to 60 parts by weight of a volatile blowing agent, having a Kauri-butanol value up to 25, in an extruder at high temper-ature and pressure, and extruding the resulting blended mixture into a zone kept under a pressure which is not higher than atmospheric pressure, thereby allowing the extrudate to expand.
2. A process as in Claim 1 employing 30 to 90 weight percent of an ionomer resin and 70 to 10 weight percent of a styrenic synthetic resin.
3. A process as in Claim 1 wherein the styrenic synthetic resin is polystyrene.
4. A process as in Claim 1 wherein the styrenic synthetic resin contains 3 to 80 weight percent of a rubbery substance.
5. A process as in Claim 1 wherein the melt index of the styrenic synthetic resin is from 0.3 to 30 g/10 min.
6. A process as in Claim 1 wherein the melt index of the ionomer resin is from 0.3 to 10 g/10 min.
7. A process as in Claim 1 wherein the melt index of the ionomer resin is from 0.3 to 2.9 g/10 min.
8. A process as in Claim 1 wherein the volatile blowing agent is a mixture containing:
1) 20 to 90 weight percent of at least one member selected from the group consisting of volatile blowing agents having Kauri-butanal values up to 25 and normal boiling points up to 90°C, together with 2) 80 to 10 weight percent of at least one member selected from the group consisting of blowing agents having Kauri-butanal values of at least 26 and normal boiling points up to 90C.
1) 20 to 90 weight percent of at least one member selected from the group consisting of volatile blowing agents having Kauri-butanal values up to 25 and normal boiling points up to 90°C, together with 2) 80 to 10 weight percent of at least one member selected from the group consisting of blowing agents having Kauri-butanal values of at least 26 and normal boiling points up to 90C.
9. A process as in Claim 1 wherein the blended mixture is extruded at a temperature of from 70°C to 100°C.
10. A process as in Claim 8 wherein the blended mixture is extruded at a temperature of from 85°C to 100°C.
11. A process as in Claim 1 wherein the extrudate has a thickness of from 0.5 mm to 100 mm, and is allowed to expand to an expansion ratio of from 2 to 50 to produce a foamed article having a thickness of from 1 mm to 1000 mm.
12. A process as in Claim 11 wherein the thickness of extrudate is from 2 mm to 50 mm and the thickness of the foamed article is from 20 mm to 1000 mm.
13. A foamed article having a bulk density from 15 to 200 Kg/m3 comprising a foamed resinous composition containing 10 to 90 weight percent of an ionomer resin having a melt index of from 0.1 to 50 g/10 min. and 90 to 10 weight percent of a styrenic synthetic resin.
14. A foamed article as claimed in Claim 13 having a bulk density from 20 to 50 Kg/m3 containing 40 to 70 weight percent of ionomer resin and 60 to 30 weight percent of styrenic synthetic resin, the said styrenic synthetic resin containing at least 70 weight percent of a member selected from the group consisting of styrenic and styrene derivatives, said foamed article having a thickness of from 20 mm to 1000 mm and the following properties:
a. Compression strength from 2 to 4 Kg/cm2;
b. Compression recovery from 80 to 99%;
c. Deceleration from 100 to 50;
d. Heat transfer ratio from 0.031 to 0.020 Kcal/m/hour°C.
a. Compression strength from 2 to 4 Kg/cm2;
b. Compression recovery from 80 to 99%;
c. Deceleration from 100 to 50;
d. Heat transfer ratio from 0.031 to 0.020 Kcal/m/hour°C.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3575875A JPS5316826B2 (en) | 1975-03-25 | 1975-03-25 | |
| JP50123546A JPS5247863A (en) | 1975-10-14 | 1975-10-14 | Process for manufacturing thermoplastic resin foam |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1073620A true CA1073620A (en) | 1980-03-18 |
Family
ID=26374753
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA248,591A Expired CA1073620A (en) | 1975-03-25 | 1976-03-23 | Extrusion foamed article and process for producing the same |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1073620A (en) |
| DE (1) | DE2612361C3 (en) |
| FR (1) | FR2305293A1 (en) |
| GB (1) | GB1517463A (en) |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1532472A (en) * | 1967-05-26 | 1968-07-12 | Pechiney Saint Gobain | Process for the preparation of foams of unplasticized polymer or copolymer compositions, based on vinyl chloride, by extrusion, and foams of low densities resulting therefrom |
| DE1704479C3 (en) * | 1967-06-16 | 1975-08-14 | Basf Ag, 6700 Ludwigshafen | Open-cell foams made from ethylene copolymers |
| JPS4935471A (en) * | 1972-08-07 | 1974-04-02 | ||
| JPS5721453B2 (en) * | 1973-07-06 | 1982-05-07 |
-
1976
- 1976-03-23 GB GB11654/76A patent/GB1517463A/en not_active Expired
- 1976-03-23 CA CA248,591A patent/CA1073620A/en not_active Expired
- 1976-03-24 DE DE2612361A patent/DE2612361C3/en not_active Expired
- 1976-03-25 FR FR7608745A patent/FR2305293A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FR2305293B1 (en) | 1979-04-20 |
| DE2612361B2 (en) | 1981-04-30 |
| FR2305293A1 (en) | 1976-10-22 |
| GB1517463A (en) | 1978-07-12 |
| DE2612361A1 (en) | 1976-10-07 |
| DE2612361C3 (en) | 1982-03-18 |
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