CA1122350A - Compositions for polyvinyl chloride resin foams - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A resin composition expandable into a foam by heating which comprises: 100 parts by weight of a polyvinyl chloride-based resin having an average degree of polymerization not exceeding 2,000 and a pore volume not exceeding 0.20 ml/g; and at least 1 part by weight of a hydrocarbon or a halogenated hydrocarbon having a boiling point not exceeding 90°C and impregnated in the polyvinyl chloride-based resin as a volatilizable foaming agent. The resin composition is improved by the incorporation of 0.5 to 30 parts by weight of an acrylic resin or a styrene-based resin. The composition is further improved by the incorporation of 0.01 to 20 parts by weight of a nucleating agent. The resin composition provides foams of high expansion, very fine and uniform cell structure and free from undesirable coloration.

Description

The present invention relates to a composition suitable for manufacturing a polyvinyl chloride-based resin foam.
In the prior art, polyvinyl chloride-based resin foams (hereinafter abbreviated as PVC resin foams) have been manufactured by several different processes. For example, (1) the resin is blended or impregnated with a decomposable foaming agent, which is a compound decomposable at an elevated tempera-ture with evolution of a gas, and the resin blend is fabricated with heating by the techniques of extrusion molding, injection molding or other conventional molding means whereby the resin is expanded into a foam by the gas produced by the decomposition of the foaming agent; (2) a so-called plastisol of pasty consistency is first prepared by admixing the resin with a plasticizer and the plastisol is processed into a foam with entrainment of air by a suitable mechanical means or, alternatively, the plastisol is further admixed with a decomposable foaming agent and the blend is heated, whereby, the foaming agent is decomposed to produce a gas simultaneously ; with the gelation of the plastisol; (3) a resin blend containing a decomposable foaming agent is first fabricated into shaped ` articles such as plates, slabs, rods, tubes and the like by rolling or other suitable mechanical means at a temperature lower than the decomposition temperature of the foaming agent and then the shaped articles are heated to effect expansion into foam by the decomposition of the foaming agent; or (4) a metal mold is filled with a resin blend containing a decomposable foaming agent, optionally, with admixture of a volatilizable foaming agent, an organic solvent with which the resin is swellable and a softening agent, and the resin blend is heated under pressure in the metal mold, to produce a melt which gells, `:
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, 112Z3S() followed by cooling to room temperature while still in the metal mold and under pressure to give a shaped article, which is subse~uently heated again at a temperature higher than the softening temperature of the resin to effect expansion of the resin blend into a foam with the gas produced by the decomposi-tion and/or vaporization of the foaming agents.
As is understood from the above description, the gas as the entity which effec~s expansion of the resin blend and is confined in the PVC resin foam is mostly either the atmospheric air entrained by a mechanical means or a gas which is a decomposition product of the decomposable foaming agent. The mechanical entrainment of atmospheric air is, however, unsatisfactory because foams of fine and uniform cell structure and high expansion can not readily be obtained even by the use of a very elaborate mixing apparatus. The use of a decomposable foaming agent is undesirable when a white PVC resin foam is desired, because, most of the practically employed decomposable foaming agents are azo compounds which form colored decomposition products leading necessarily to yellowish or brownish coloring of the resin foam manufactured therewith. Furthermore, the cell structure of a resin foam obtained with a decomposable foaming agent is not always satisfactory in its fineness and uniformity, especially, when a resin foam of high expansion is desired.
In addition to the above drawbacks, the above described methods (1) to (3) are not suitable for the preparation of rigid or semi-rigid foams of high expansion, i.e.
the methods are limited to the manufacture of soft or flexible resin foams; and method (4) is disadvantageous from the stand-point of efficiency and production cost as the process must be

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l~Z23~0 carried out batch-wise and the time taken for the preparation of a batch of the foam is long due to the complexity of the process.
Another source of gas for resin foams is a volatilizable foaming agent which is a compound of relatively low boiling point and which is readily converted to a gas when the resin blend containing it is heated. Thus, if the heating temperature is above the softening point of the resin, resin foams are obtained. This class of foaming agents is desirable owing to the absence of colored decomposition products, leading to the coloration of the resin foams, since the formation of the gas is effected not by the decomposition but merely by the vaporization of the foaming agent.
; The use of a volatilizable foaming agent has been successful in the manufacture of several kinds of plastic foams such as polystyrene resin foams, but no successful process has been developed hitherto for the preparation of PVC resin foams, although the reason for the difficulty has not yet been completely analyzed.
Thus, an object of the present invention is to provide a composition suitable for manufacturing PVC resin foams containing a foaming agent of the volatilizable type.
According to an aspect of the invention there is provided a resin composition expandable into a foam by heating which comprises 100 parts by weight of a polyvinyl chloride-based resin having an average degree of polymerization not exceeding 2,000 and a pore volume not exceeding 0.20 ml/g; and at least 1 part by weight of a volatilizable foaming agent selected from the group consisting of a hydrocarbon, a halogenated hydrocarbon and mixtures thereof having a boiling point not exceeding 90C
and impregnated in said polyvinyl chloride-based resin.

The main ingredient of the compositions described herein is a PVC resin which may be a homopolymer or a copolymer mainly composed of vinyl chloride. When the PVC resin is a copolymer, it is preferable that the proportion of the monomer or monomers copolymerized with vinyl chloride not exceed 40% by weight or, in other words, at least 60% by weight of the resin constituents should be vinyl chloride, from the standpoint that the resultant resin foams may have excellent flame retardancy, high mechanical strength and other desirable properties inherent to vinyl chloride resins.
The ethylenically unsaturated monomers copolymerizable with vinyl chloride are well known in the art as exemplified by vinyl esters such as vinyl acetate and vinyl propionate;
vinylidene halides such as vinylidene chloride and vinylidene fluoride; vinyl halides other than vinyl chloride such as vinyl fluoride; acrylic acid and esters thereof such as ethyl acrylate; methacrylic acid and esters thereof such as methyl methacrylate; acrylonitrile, methacrylonitrile; maleic acid - and esters and anhydride thereof; fumaric acid and esters ; 20 thereof; and olefins such as ethylene and propylene.
Among the above named comonomers, vinyl acetate is most preferred since a copolymer of vinyl chloride and vinyl acetate not only is susceptible to impregnation with a foaming agent but also has a markedly reduced melt viscosity so that smoothness in foaming is ensured leading to the formation of resin foams with a further improved fine and uniform cell structure. In order that such an advantageous effect can be expected by the use of the copolymer, the content of vinyl acetate in the copolymer resin is preferably at least 3~ by weight with the upper limit being 40~ by weight as set forth above.

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The essential parameters for the PVC resins used in the resin compositions described herein are the average degree of polymerization and the pore volume. The average degree of polymerization, which is readily determined by the measurement of the solution viscosity of the resin, preferably does not - exceed 2,000since a PVC resin having an average degree of polymerization larger than 2,000 has an extremely high melt viscosity and poor gelation so that resin foams of high expansion can not readily be obtained even with a large amount of the foaming agent impregnated in the resin. On the other hand, the lower limit of the average degree of polymerization is deter-- mined in consideration of the desired mechanical properties of the resin foams prepared with the resin. For example, a PVC resin having an average degree of polymerization of less than 300 can only give fragile and mechanically inferior resin foams.
The other important parameter for the PVC resin is the pore volume which preferably does not exceed 0.20 ml/g or, more preferably, 0.10 ml/g of the resin. This value of the pore volume is rather small in comparison with ordinary PVC
resins which have pore volumes of about 0.25 ml/g or more, when the resin is a homopolymer of vinyl chloride. The pore volume is a value determined with a mercury-pressurizing porosimeter where the mercury pressure is increased from 1 to 100 kg/cm2 so - that the mercury is forced into pores of the resin particles having a pore diameter of about 30 ~m or less.
The above limitation of the pore volume is essential because a PVC resin having a larger pore volume is poor in retention of the foaming agent and permits dissipation of the foaming agent not only during storage of the resin composition ~, impregna-ted with the foaming agent but also in the molding process of the resin composition into a shaped article of resin foam, hence, foamed bodies of high expansion can not readily be obtained.
The PVC resins which can meet the above requirements are obtained by the suspension polymerization of vinyl chloride ;:
monomer or a monomer mixture mainly composed of vinyl chloride monomer in an aqueous medium containing a suspending agent in the presence of a free radical polymerization initiator soluble in the monomer phase.
The volatilizable foaming agent to be impregnated in the above described PVC resins is, as mentioned above, a hydro-carbon or a halogenated hydrocarbon compound having a boiling point not exceeding 90C or, preferably, not exceeding 70C.
~hen a foaming agent having a boiling point higher than 90C
is employed, the resin foams once expanded exhibit extensive shrinkage upon standing so that the resultant foamed body has an unsatisfactory cell structure in respect of fineness and uniformity.
The hydrocarbon or halogenated hydrocarbon compounds suitable for use as a foaming agent in the compositions described ; herein are exemplified by propane, butane, isobutane, pentane, neopentane, n-hexane, isohexane, n-heptane, methyl chloride, methylene chloride, chloroform, carbon tetrachloride, ethylidene chloride, ethylidene fluoride, trichloroethylene, 1,2-dichloro-ethane, trichlorofluoromethane, dichlorodifluoromethane, chlorotrifluoromethane, bromotrifluoromethane, tetrafluoro-methane, dichlorofluoromethane, chlorodifluoromethane, trifluoro-methane, trichlorotrifluoroethane, dichlorotetrafluoroethane, dibromotetrafluoroethane, chloropentafluoroethane, hexafluoro-L~

ethane, l-chloro-l,l-difluoroethane and the like. These volatilizable foamlng agents may be used in cornbination.
The extent of impregnation of the PVC resins with the above mentioned volatilizable foaming agents depends on the - desired degree of expansion into resin foams. Generally, the degree of impregnation must be increased when a foamed body of high expansion ratio is desired. When a foamed body of low expansion is desired, 3~ by weight or less of a foaming agent may sometir,les be sufficient. The amount of the foaming agent is, however, in the range from 1 to 30% by weight or more in most cases where foamed bodies of adequate expansion are to be obtained.
The impregnation of the PVC resin with a volatilizable foaming agent noted above is carried out in principle by bringing these components into contact with each other.
Particularly, the PVC resin in a powdery form may merely be blended with the foaming agent so that the foaming agent is absorbed in the resin particles. When the foaming agent is gaseous at room temperature and under atmospheric pressuré, a convenient method for impregnation is to introduce the PVC
resin, water and dispersing agent into a pressurizable vessel, e.g. an autoclave, equipped with a stirrer to forrn a suspension of the resin powder in the aqueous medium and then the foaming agent is introduced into the suspension with pressurization followed by agitation of the mixture at temperatures of 30 to 90 C for 3 to 20 hours. After absorption equilibrium has been established inside the vessel and the mixture is cooled to room temperature, the resin having absorbed the foaming agent is taken out of the vessel, dehydrated by a suitable means, such as centrifugal separation, and dried under air flow at a B

relatively low temperature of, say, 50C or less to give the desired PVC resin impregnated with the foaming agent.
The thus prepared resin composition impregnated with the volatilizable foaming agent can be, as such, fabricated into shaped resin foam articles by a conventional technique such as injection molding, extrusion molding or compression molding in a metal mold in which gelation of the resin and expansion of the gelled resin by the gas produced by the vaporization of the foaming agent take place simultaneously. It is optional that the resin composition be, prior to fabrication, admixed with additives conventionally used in the molding of PVC resins, such as plasticizers, flame retardants, anti-oxidants, anti-static agents and the like, at a relatively low temperature to prevent premature vaporization of the foaming agent.
As mentioned earlier, one of the problems in obtaining a foamed PVC resin body is to ensure fineness and uniformity of the cell structure of the resin foam, especially, when the ratio of expansion of the foam is extremely high or when the foam has a bulk density of, for example, 0.10 g/cm3 or less.
Of course, depending on the manufacturing conditions, the foams could have a bulk density of about 0~30 g/cm3. Improvement of the cell structure of PVC resin foams is expected through the use of foam conditioning agents. This invention discloses certain types of thermoplastic resins as particularly effective foam conditioning agents.
The foam-conditioning resins disclosed herein include acrylic resins and styrene-based resins and these resins are particularly effective when they have a reduced viscosity of at least 3.0 dl/g as measured in a chloroform solution of 0.1 g/100 ml concentration at 25C. These foam-conditioning resins are '~

11223~0 blended with the PVC resin impregnated with the volatilizable foaming agent in an amount of from 0.5 to 30 parts by weight per 100 parts by weight of the PVC resin impregnated with the foaming agent before the resin composition is molded into shaped resin articles.
An acrylic resin suitable as the foam-conditioning resin is either a polymethyl methacrylate or a copolymeric resin mainly composed of methyl methacrylate and one or more of acrylic esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate and the like. The content of methyl methacrylate in the acrylic resin is preferably in the range from 60 to 95% by weight.
It is preferable that the acrylic resin, as the foam-conditioning resin, have a reduced viscosity of at least 3.0 dl/g, or, more preferably, at least 5.0 dl/g as measured in a chloroform solution of 0.1 g/100 ml concentration at 25C.
It is preferable to use an acrylic resin with a higher reduced viscosity or, in other words, having a higher average degree of polymerization when the average degree of polymeriza-tion of the PVC resin approximates the upper limit of 2,000.
Further, it is preferable to use an acrylic resin prepared by the emulsion polymerization of the acrylic monomers. Additional improvements are obtained by the use of such a resin, e.g., in the smoothness of feeding into a molding machine, which reduces the danger of blockage of the inlet for the resin composition fed to the machine, in addition to the acceleration of uniform gelation of the resin composition and increased expandability of the gelled and molten resin composition.
The amount of the acrylic resin, as the foam-.~' l~Z~350 conditioning agent, to be admixed is from 0.5 to 30 parts by weight or, preferably, from 3 to 20 parts by weight per 100 parts by weight of the PVC resin impregnated with the foaming agent.
Larger amounts of the acrylic resin than noted above cannot give any further improvement and, instead, undesirably effect the properties inherent to PVC resins such as flame retardancy.
Styrene-based resins is the other class of foam-conditioning resins. The styrene-based resin may be a homo-polymer of styrene but it is preferably a copolymer mainly composed of styrene with a minor amount of acrylonitrile as the comonomer. It is, of course, optional that the copolymer include one or more of other comonomers copolymerizable with styrene and acrylonitrile. The styrene-based resin should have a reduced viscosity of at least 3.0 dl/g as measured in a chloroform solution of 0.10 g/100 ml concentration at 25 C. It is preferable that the styrene-based resin have a reduced viscosity as high as possible when the vinyl chloride-based resin has an average degree of polymerization approximating the upper limit of about 2,000.
The above mentioned comonomers copolymerizable with styrene and acrylonitrile are exemplified by esters of acrylic acid such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate and the like; esters of methacrylic acid such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate and the like; maleic and fumaric acids and esters thereof and maleic anhydride.
The above described styrene-based resins can be prepared by a conventional method of polymerization but it is preferable that the resins be prepared by emulsion polymerization in an aqueous medium.

~' 1~22350 The amount of the styrene-based resin to be used, as the foam~conditioning agent, may be the same as with the acrylic resins, i.e. in the range from 0.5 to 30 parts or, preferably, from 3 to 20 parts by weight per 100 parts by weight of the PVC resin impregnated with the volatilizable foaming agent.
The mechanism by which the improvement is obtained in the cell structure of the resin foams by the addition of the foam-conditioning resin is presumably that: the gelation of the PVC resin is accelerated by the foam-conditioning resin and the melt viscosity of the PVC resin in the molding step is adequately controlled or increased so that the expandability of the foams is enhanced and the cell walls of the foams are strengthened to have a higher resistance against coalescence or collapse of the foams as well as that the shrinkage of the once formed foams at an elevated temperature is prevented with improved retention of the gas produced by the vaporization of the foaming agent.
It was further discovered that the above described foam-conditioning effect obtained by the addition of a foam-conditioning resin is further enhanced when certain kinds of nucleating agents are present in combination with the foam-conditioning resin. One type of suitable nucleating agent is a fine powdery inorganic material such as calcium carbonate, talc, barium sulfate, fumed silica, titanium dioxide, clay, aluminum oxide, bentonite, diatomaceous earth and the like having an average particle diameter of 30 ~m or less, or preferably, 10 ~m or less. Coarser particles of these inorganic powders affect the fluidity of the molten resin in the molding step adversely so that the surface condition of the foamed bodies obtained with admixture of such coarser powders is deficient in luster, sometimes, with striation and inferior uniformity of the cell structure.

1~223~0 Another class of suitable nucleating agents is the product of the combination in about equivalent amounts of an acid such as boric acid or organic acids, e.g. citric acid, tartaric acid and oxalic acid and a carbonate or hydrogencarbonate of sodium, potassium or ammonium such as sodium carbonate, sodium hydrogencarbonate, potassium carbonate, ammonium hydrogencar-bonate and the like.
The amount of the nucleating agent to be added in combination with the foam-conditioning resin is in the range from 0.01 to 20 parts by weight per 100 parts by weight of the PVC resin impregnated with the foaming agent. When the amount of the nucleating agent is in excess of 20 parts by weight, the ratio of expansion of the foamed resin is decreased and the resultant foamed body has inferior properties including less smooth surfaces.
It is optional that the resin composition described herein be admixed with a known decomposable foaming agent in so far as the amount thereof is limited to, say 5 or less parts by weight per 100 parts by weight of the PVC resin impregnated with the volatilizable foaming agent. A suitable decomposable foaming agent is exemplified by azo compounds such as azodicarbonamide, azobisisobutyronitrile, diazoaminobenzene, diethylazodicar-boxylate, diisopropylazodicarboxylate and the like; nitroso compounds such as N,N'-dinitrosopentamethylene tetramine, N,N'-dimethyl-N,N'-dinitroso terephthalamide and the like; and sulfonylhydrazide compounds such as benzenesulfonylhydrazide, toluenesulfonylhydrazide, 4,4'-oxy-bis(benzenesulfonylhydrazide),

3,3'-di(sulfonehydrazidephenyl)sulfone, toluenedisulfonyl-hydrazone, thio-bis(benzenesulfonylhydrazide), toluenesulfonyl-azide, toluenesulfonyl semicarbazide, 4,4'-oxy-bis(benzene-sulfonylhydrazide) and the like; as well as sodium hydrogen-3~;0 carbonate.
The use of these decomposable foaming agents isdesirable in order to further improve the fineness and uniformity of the cell structure of the resin foams and to reduce the shrinkage of the foamed body so that the shape of the foamed body is better retained. However, the use of too much of a decomposable foaming agent is undesirable due to the coloration of the foamed body by the colored decomposition products thereof and the roughened surface condition of the foamed body without additional advantages. It is also preferable to add a conventional decomposition promotor such as certain kinds of zinc compounds, copper compounds and the like to accelerate the decomposition of the decomposable foaming agent and enhance gas evolution at a temperature lower than the molding temperature of the resin composition.
The above described expandable resin compositions with admixture of a foam-conditioning resin are advantageous for manufacturing shaped bodies from PVC resin foams. The composi-tions can give resin foams of high expansion with fine and uniform cell structure regardless of the rigidity of the desired foamed products, which can range from soft and flexible to hard and rigid, by any one of conventional continuous fabrication procedures including extrusion molding, injection molding, compression molding and the like without any extra cost.
In the following, examples of the present invention are given to ilLustrate the invention in further detail. In the examples all parts are by weight. The methods for the deter-mination of the degree of impregnation of the volatilizable foaming agent in the PVC resin and the pore volume of the resin are as follows.

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Amount of impregnation of the volatilizable foaming àgent: the PVC resin impregnated with the volatilizable foaming agent was heated in an air oven at 130C for 2 hours and the amount of impregnation was calculated by the equation (Wl - W2)/W2 x 100 (~), taking the weights before and after heating as Wl and W2, respectively.
Pore volume of the PVC resin: the pore volume was determined with a mercury-pressurizing porosimeter, Model 70 made by CARL ERBA Co., where the pressure of mercury was increased from 1 to 100 kg/cm2 and expressed in ml per gram of the resin.

EXAMPLE 1 (Experiments No. 1 to No. 13) Into an autoclave of 5 liter capacity equipped with a stirrer were introduced 1,000 g of a vinyl chloride homopolymer or a copolymer resin composed of vinyl chloride and vinyl acetate as indicated in Table 1, in which P and Vp stand for the average degree of polymerization and the pore volume of the resin, respectively, and 2,000 g of purified water; then 150 g of trichlorofluoromethane and 200 g of butane were introduced into the autoclave with pressurization followed by temperature elevation with agitation up to 70C and continued agitation at the same temperature for 8 hours to impregnate the resin with trichlorofluoromethane and butane as the volatilizable foaming agents.
After cooling to room temperature and discharging the excess foaming agents out of the autoclave, the thus impregnated resin was taken out of the autoclave, dehydrated and dried under air flow at 40 to 50C for about 8 hours.
The degree of impregnation of the resin with the ~2Z35~

foaming agents was determined just after preparation and after storage at 20C for 1 week to give the results set out in Table 1.
100 parts of the above obtained resin impregnated with the foaming agents was blended with 2 parts of a tin-containing stabilizing agent and 1 part of calcium stearate and the resin blend was fabricated into a foamed cylindrical rod by extrusion molding with an extruder machine operated with the conditions given below.
The bulk density of the foamed rod obtained in each ~-of the experiments was as given in Table 1.
Operating conditions of the extruder machine:

Screw diameter 20 mm Screw length 400 mm Screw compression ratio 3.0 Die 5 mm diameter opening and 70 mm land length Screens one with 80 mesh opening and one with 100 mesh opening Cylinder temperature Cl = 60 to 120C
C2 = 100 to 160C
C3 = 120 to 180C
Die temperature about 130 C
Revolutions 50 r.p.m.

The foamed rod obtained in Experiment No. 9 was very fragile. Although the foamed rod obtained in Experiment No. 11 had a high ratio of expansion, it was inferior in flame retardancy.

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_ E C 3 - la ~ 3 m o h ~' ~2Z3S~) EXAMPLE 2 tExperiments No. 14 to No. 26) Into the autoclave used in Example 1 were introduced 1,000 g of a copolymer resin composed of 88% by weight of vinyl chloride and 12~ by weight of vinyl acetate, and having a pore volume, Vp, of 0.010 ml/g and an average degree of polymerization P, of about 650, 2,000 g of purified water and 1.0 g of a partially saponified polyvinyl alcohol; and then one or two volatilizable foaming agent(s) as indicated in Table 2 in amounts also as indicated in Table 2 were introduced into the autoclave, if necessary, with pressurization followed by agitation for 8 hours at 70C to impregnate the resins with the foaming agent(s).
The notations for the volatilizable foaming agent(s) used in this Example are as follows and will hereafter be used in other examples.
PR: propane PE: pentane HE: n-hexane TCFM: trichlorofluoromethane MC: methyl chloride BU; butane MEC: methylene chloride DCTFE: dichlorotetrafluoroethane DCDFM: dichlorodifluoromethane DCFM: dichlorofluoromethane TCE: 1,1,2-trichloroethane TCDFE: tetrachlorodifluoroethane ISO: isooctane The degree of impregnation with the foaming agent(s) and the bulk density of the foamed cylindrical rods, fabricated ~llZZ350 in the same manner as in Example 1, were as set out in Table 2.
The foamed rods in Experiments Nos. 24 to 26 exhibited large shrin~age after molding.

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EXAMPLE 3 (Experiments No. 27 to No. 33) Into a 100 liter capacity autoclave made of stainless steel and equipped with a stirrer were introduced 30 kg of the vinyl chloride and vinyl acetate copolymer resin used in Example 2, 50 kg of purified water and 15 g of a partially saponified polyvinyl alcohol; and further a mixed foaming agent composed of butane and trichlorofluoromethane in a 2:1 ratio was introduced with pressurization into the autoclave in an amount as indicated in Table 3, followed by agitation for 8 hours at a temperature also as indicated in Table 3 to impregnate the resin with the foaming agent. The dehydration and drying of the resin impregnated with the foaming agent were undertaken in the same manner as in Example 1. The degree of impregnation with the foaming agent was as set out in Table 3.
Resin blends were prepared each with 100 parts of the above obtained resin impregnated with the foaming agent, 2 parts of a tin-containing stabilizing agent and 1 part of calcium stearate and the resin blend was fabricated into a foamed body in the form of a slab by extrusion molding with an extruder machine operated with the conditions as given below.
The bulk density, heat conductivity, as measured at 20C according to the method specified in JIS A 1413, and compression strength, as measured at 20C according to the method specified in ASTM D 1621, of the foamed slabs were determined to give the results sèt out in Table 3.
Operating conditions of the extruder machine:
Screw diameter 65 mm Screw length 1,300 mm Screw compression ratio 2.0 Z3S~

Die 100 mm width and 8 mm height Screens one with 80 mesh opening and one with 100 mesh opening Cylinder temperature Cl = 80C
C2 = 120C
C3 = 150C
Die temperature 120 C
Revolutions 30 r.p.m.

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r~ c~ 6 ~ ~ H 3 la 3 ....

E~7 ~LlZ23~i0 EXAMPLE 4 (Experiments No. 34 to No. 43) The proceduxe of Example 1 for the preparation of a vinyl chloride and vinyl acetate copolymer resin impregnated with a mixed foaming agent of trich~orofluoromethane and butane was repeated; where the resin used had a vinyl acetate content, average degree of polymerization, P, and pore volume, Vp, as indicated in Table 4. The degree of impregnation with the foaming agent as determined just after preparation and after storage for 1 week at 20C were as set out in Table 4.
Expandable resin compositions were prepared each by blending 100 parts of the above prepared copolymer resin irnpregnated with the ~ixed foaming agent, 2 parts of a tin-containing staiblizing agent and 1 part of calcium stearate along with or without the addition of 1 part of talc, as the nucleating agent, 1 part of an azodicarbonamide compound, CELMIC 133 a trade mark of Sankyo Kasei Co., Japan, as a decomposable foaming agent, and either one of the acrylic resins E-l and E-2 as defined below in an amount given in Table 4.
The acrylic resins used as the foam-conditioning agent in the experiments and designated as E-l or E-2 in Table 4 were the following products, respectively:
E-l: a copolymeric resin composed of 90% by weight of methyl methacrylate and 10% by weight of ethyl acrylate and having a reduced viscosity of 10 dl/g at 25C in a 0.1 g/100 ml chloroform solution, and E-2: an acrylic resin commercially available under the trade mark PARALOID K-120 from Rohm & Haas Co .

~"7 l~ZZ35~J

The expandable resin compositions were fabricated into foamed rods by extrusion molding with theJex~ruder machine and operating conditions used in Example l; and the foamed rods were examined for bulk density and cell structure to give the results as set out in Table 4. The evaluation of the cell structure given in Table 4 was determined according to the following standards.
Cell structure A: cell diameter not exceeding 500 ~m Cell structure B: cell diameter from 500 ~m to 2,000~m The foamed rod obtained in Experiment No. 40 was fragile. In Experiment No. 43 premature expansion of the resin composition took place while still in the die leading to the appearance of flow marks on the surface of the foamed rod.

B?

Table 4 Experiment No. 34 35 36 37 38 Content of vinyl acetate, % by12 12 5 20 30 PVC weight resin p 520 520 350 700 1000 Vp, ml/g 0.010 0.010 0.009 0.0120.020 Impre~ nation As 11 0 11 0 8.0 10.3 7.5 with mixed prepared . .
foaming weight Alt r 10.3 10.3 7.4 9.7 7.0 Nucleating agent Yes Yes Yes Yes Yes Decomposable No Yes Yes Yes Yes foaming agent Acrylic resin E-1 E-1 E-2 E-2 E-2 (parts) (10.0) (10.0) (6.0) (6.0) (6.0) :
t~e~ o density,0.05C 0.045 0.05C 0.051 u.10 . structure A A A A A

Cont'd.

~2Z350 Table 4 Cont'd.

0;023 0.'010 0.050 0.060 0.020 7. 9.0 6.0 6.99 5 6.6 8.0 4.0 5.48.5 Yes No No No Yes Yes No No No No E-2 None None None None 0 20 0.~4 0.30 0.23 0.11 A B B B B

D

EXAMPLE 5 (Experiments No. 44 to No. 54) Into the autoclave used in Example 1 were introduced 1,000 g of the vinyl chloride and vinyl acetate copolymer resin used in Example 2, 2,000 g of purified water and 1.0 g of a partially saponified polyvinyl alcohol; and then one or two volatilizable foaming agents as indicated in Table 5 and in amounts also as indicated in Table 5 was introduced into the autoclave with pressurization followed by agitation at 70C
for 8 hours to impregnate the resin with the foaming agent(s).
The degree of impregnation with the foaming agent(s) was as set out in Table 5.
Expandable resin compositions were prepared each by blending 100 parts of the copolymer resins impregnated with the volatilizable foaming agent(s), 1 part (Experiments No. 44 to No. 46) or 3 parts (Experiments No. 47 to No. 54) of a nucleating agent as indicated in Table 5 along with or without the addition of 6 parts of an acrylic resin (METABLEN P551, a trade mark of Mitsubishi Rayon Co., Japan) as the foam-conditioning agent.
The nucleating agents used in the experiments were as follows.
ORBEN: a trade mark of Shiraishi Calcium Co., Japan for an organic complex of a colloidal hydrated aluminum silicate having an average particle diameter of about 0,5 ~m;
HAKUENKA O: a trade mark of Shiraishi Calcium Co., Japan for a calcium carbonate filler having an average particle diameter of 0.02 to 0.03 ~m;
Titanium Dioxide A-100: a filler grade titanium dioxide havlng an average particle diameter of about 0.15 to 0.25 ~m, a product of Ishihara Sangyo Co., Japan;

B~

Z3~0 AEROSIL 200: a trade mark of Nippon Aerosil Co., Japan for a fumed silica filler having a specific surface area of about 200 m2/g and an average particle diameter of about 0.012 ~m;
AEROSIL 380: a trade mark of Nippon Aerosil Co., Japan for a fumed silica filler having a specific surface area of about 380 m2/g and an average particle diameter of about 0.002 ~m;
A12O3C: an alumina filler having an average particle diameter of about 0.005 to 0.02 ~m, a product of Nippon Aerosil Co., Japan;
Barium Sulfate #100: a product of Sakai Chemical Co., Japan, having an average particle diameter of about 0.6 ~m;
SATENTON No. 5: a trade mark of Tsuchiya Kaolin Co., Japan for a clay product;
3S Talc: a talc product of Nitto Funka Kogyo Co., Japan.

The expandable resin compositions thus prepared were fabricated into foamed bodies in the form of a cylindrical rod by extrusion molding with the extruder machine and the operating conditions used in Example 4; and the foamed rods were examined for their bulk density to give the results as set out in Table 5.

B`

~223~0 Table 5 Experiment No. 1 44 45 46 . 4~8 Volatilizable PR PE TCFM BU BU
foaming (300) (300) (300)(300) (200) agent (g) MEC
. . _ Impregnation with foaming agent, 6.5 7.0 15.4 7.3 11.0 % by weight Nucleating ORBEN ORBEN HAKU- Titanium A~ROSIL
agent ENKA A-100 200 .
Decomposable No No No No No foaming agent . _ ._ Acrylic resin Yes Yes Yes Yes Yes :~ -foamed rod, g/ml0.0890.093 0 077 0.080 0.039 Cont'd.

B`;

~l~Z350 Table 5 Cont ' d .

I l I

( 200 ) ( 30 ) ( 100 ) ( 200 ) ( 200 ) ( 200 ) PE BU BU BU
( 1 00 ) ( 3 ) ( 100 ) ( 400 ) . .__ . . . , 12.4 3.4 8.2 15.0 9.8 7.4 . . .__ .
2 Barium Talc Clay AEROS I I HAKU-3 Sulfate 380 ENKA O
# 100 .. .. __ -, ~
Yes Yes Yes Yes Yes Yes .

Yes Yes Yes Yes No No . .
59_ _ 0 . 15 0 . 073 0. 030 0 . 70 0 . 81 .

B -30_ ~Z2350 EXAMPLE 6 (Experiments No. 55 to No. 68) Into a 100 liter capacity autoclave made of stainless steel and equipped with a stirrer were introduced 30 kg of a copolymer resin composed of 884 by weight of vinyl chloride and 12~ by weight of vinyl acetate and having an average degree of polymerization, P, of about 850 and a pore volume, Vp, of 0.015 ml/g, 50 kg of purified water and 15 g of a partially saponified polyvinyl alcohol; and then 6 kg of trichlorofluoro-methane and 3 kg of butane were introduced with pressurization into the autoclave followed by agitation at 70C for 8 hours to impregnate the resin with trichlorofluoromethane and butane as the volatilizable foaming agents. After completion of impregna-tion, cooling to room temperature and discharging of excess foaming agents, the resin was dehydrated by centrifugal separation and dried under air flow at 40 to 50C. The total amount of foaming agents in the resin was 11.84 by weight.
Expandable resin compositions were prepared each by blending 100 parts of the above obtained copolymer resin impregnated with the volatilizable foaming agents, 2 parts of a tin-containing stabilizing agent and 1 part of calcium stearate along with or without the addition of talc (Experiments other than No. 59) in an amount indicated in Table 6, or a combination of 0.5 part of sodium hydrogencarbonate and 0.4 part of citric acid (Experiment No. 59) as a nucleating agent, a decomposable foaming agent and an acrylic resin as a foam-conditioning agent as given in Table 6.
The notations used in Table 6 for the decomposable foaming agents and the acrylic resins are as follows:
AIBN: ~ azobisisobutyronitrile, PTS: p-toluenesulfonyl hydrazide, l~ZZ350 OBS: 4,4'-oxy-bis(benzenesulfonyl hydrazide), DNM: dinitrosopentamethylenetetramine, and CETMIC 133: see Example 4;
E-3: a copolymer resin composed of 80% by weight of methyl methacrylate, 10% by weight of butyl acrylate and 10% by weight of ethyl acrylate having a reduced viscosity of 5.5 dl/g at 25C, E-4: a copolymer resin composed of 85~ by weight of methyl methacrylate and 15% by weight of butyl acrylate having a reduced viscosity of 5.0 dl/g at 25C, E-5: an acrylic resin commercially available under the trade mark of PARALOID K-125 from Rohm & Haas Co., and E-6: an acrylic resin commercially available under the trade mark of PARALOID K-125 from Rohm &
~aas Co.
Each of the resin compositions was fabricated into a foamed body in the form of a slab by extrusion molding with 2~ the extruder machine and the operating conditions used in Example 3; and the foamed slabs were examined for their bulk density, cell structure, appearance, compression strength, other mechanical properties and heat conductivity. The determination of the compression strength was carried out in accordance with the method specified in ASTM D 1621 and the heat conductivity was determined in accordance with the method specified in JIS A 1413. The results are set out in Table 6.
In Experiments No. 67 and No. 68, premature expansion of the resin compositions took place while still in the die leading to broken foams and appearance of flow marks on the `1 ~lZ2350 surface of the foamed slabs. The appearance of the foamed slab obtained in Experiment No. 66 was also less satisfactory. The cell structure of the foamed slabs was satisfactory in all of the experiments except that the foamed slab in Experiment No. 65 exhibited less uniformity in its cell structure.

~., llZZ35~

Table 6 Experiment No. 55 56 57 58 59 agent, parts 1.0 1.0 1.0 1.0 (Steeet) Decomposable AIBN PTS OBS DNM CEL~IC
foaming agent (1.0) (1.0) (1.0) (1.0) 133 (parts) + (1.0) Urea (1.0) Acrylic resin E-3 META- E-4 E-5 E-5 (parts) (5.0) BLEN (5.0) (1.0) (20) ; P 501 (5.) Bulk .
g/ml 0.034 0.0350.035 0.030 0.033 ~ ..
compression PirepseOrf kg/cm~ 3.3 3.5 3.5 3.0 3.4 folaabed strength,5.1 5.4 5.4 4.8 5.3 Tensile kg/cm~ 5.0 5.2 5.3 4.8 5.1 Heat con-ductivity,0.025 0.0260.026 0.025 0.028 kcal/m.hr.~C .

Cont'd.

B~

Table 6 Cont'd.

l.0 0.02 15 1.0 1.0 0.005 30 1.0 1.0 AIBN None None ELMIC CELMIC None None CELMIC CELMIC
(1.0) (335) (330) (330) 1330) E-5 E-5 E-5 E-6 E-6 E-3 E-3 E-3 E_3 (30) (10) (25) (10) (10) (5.0) (5.o)(5.0 (0.3) 0.035 0.034 0.040 0.033 0.045 0.070 0.059o.oao o .095 .
3.8 3.6 4.8 3.3 5.0 7.3 6.0 7.3 12.4 6.7 6.5 7.8 5.5 8.1 10.3 8.8 13.0 20.l 5.5 5.4 7.0 5.3 7.8 10.5 9.0 16.8 21.3 .
0.028 0.027 0.029 0.028 0.031 0.037 0.035 0.038 0.043 B` - 35 _ ~lZZ3~(~

EXAMPLE 7 (Experiments No. 69 to No. 89) Into an autoclave of 5 liter capacity made of stainless steel and equipped with a stirrer were introduced 1,000 g of a homopolymeric polyvinyl chloride resin or a copolymer resin composed of vinyl chloride and vinyl acetate as indicated in Table 7, 2,000 g of purified water, and one or two volatilizable foaming agents as indicated in Table 7 in amounts also as given in Table 7 with, if necessary, pressurization followed by agitation at 70C for 8 hours to impregnate the resins with the volatilizable foaming agent(s).
After completion of impregnation, cooling to room temperature and discharging of excess foaming agent(s), the resins were dehydrated by filtration and dried under air flow at 40 to 50C
for about 5 hours. The resins thus obtained were examined for the amount of foaming agent(s) contained therein to give the results as set out in Table 7. Further, the resins were kept at 20C for 1 week to examine the foaming agent(s) loss by dissipation during storage. The decrease in the amount of foaming agent(s) ranged from 6 to 9~ for each of the resins.
Expandable resin compositions were prepared each by blending 100 parts of the above obtained resins impregnated with the volatilizable foaming agent(s), 2 parts of a tin-containing stabilizing agent and 1 part of calcium stearate along with or without the addition of a nucleating agent, a decomposable foaming agent and an acrylic resin (E-l) as the foam-conditioning agent as indicated in Table 7. The resin compositions were each fabricated into a foamed body in the form of a cylindrical rod by extrusion molding. The operating conditions of the extruder machine were as follows:

~' 23~0 Operating conditions of the extruder machine:
Screw diameter 25 mm Screw length 750 mm Screw compression ratio 3.0 Die 8 mm diarneter opening and 100 mm land length Screens one with 80 mesh opening and one with 100 mesh opening Cylinder temperature Cl = 60 to 120C
C2 = 100 to 160C
C3 = 120 to 180C
Die temperature 100 to 130 C
Revolutions 50 r.p.m.
The thus obtained foamed rods were examined for bulk density and the condition of their cell structure to give the results as set out in Table 7.
The cell structure C indicates that the foam cells had a diameter exceeding 1 mm and the structure was coarse and not uniform. I
The foamed rod obtained in Experiment No. 84 was fragile and the foamed rods obtained in Experiments No. 88 and No. 89 exhibited shrinkage after molding.

., ~2Z350 Table 7 _ I . .... .__ Experiment No. 69 70 71 72 73 74 . . .
Content of vinyl acetate, 5 10 0 10 10 10 % by weight PVC ____ .
resin P 400 750 750 1000 1000 1000 Vp, ml/g 0.011 0.013 0.060 0.025 0.025 0.025 Volatilizable TCFM TCFM TCFM TCFM TCFM TCFM
foaming agent (150) (150)(150) (150) (150) (150) used (g) + + + + + +
BU BU BU BU BU BU
(100) (100)(100) (100) (100) (100) .
Impregnation with foaming agent, % by 11.0 10.8 7.8 9.7 9.7 9.7 weight . __ . .
Nucleating Talc Talc Talc HAKU- oRsE~ Talc agent (parts) (1.0) (1.0) (1.0) ENKA (5) (0.5) (parts~ None C(330) (OT03(OB5N)(0 5) (2) i '''' -~ ~~~~~--I 1 ~ I 1 0 ~
~roper- Bulk ties of density, 0.065 0.045 0.0600.054 0.052 0.053 foamed g/ml rod . .
_ ~ structure A A A A A A

) Sodium hydrogerlcarbonate Cont'd.

1122~0 Table 7 Cont'd.

. .
0.025 0.029 0.015 0.015 0.015 0.015 0.015 0.015 0.015 TCFM TCFM PR BU PE TCFM TCFM TCFM TCFM
(l~0) (150) (300) (3) (30) (3) (3) (100) (200) BU BU BU BU BU
(100) (100) (300) (100) (400) 9.7 9.3 6.5 7.5 8.3 15.6 3.4 8.6 15.0 Talc Talc Talc Talc Talc Talc Talc Talc Talc (0.05) (1.0) (0.5) (0.5) (1.0) (1.0) (1.0) (1.0) (1.0) ~_ SHC None None None CELMIC CELMIC CELMI CELMIC CELMIC
(5)133 133 133 133 133 (2.0) (0.5) (~.5) (0.5) (0.5) ~0 5 5 5 5 5 0.0460.0680.0800.071 0.0850.0580.0900.069 0.045 .... .
A A A A A A A A A

Cont'd.

~122350 Table 7 Cont'd.

_ 85 86 ¦ ~7 8~ ¦ ag lo 10 1'-290 ~00 1700 2100 850 850 0.0l5 0.030 0.25 0.12 0.015 ~.015 (150) (150) (150) (150) (200) (200) BU BU BU BU
(200) (200) (200) (200) 9.0 7.8 2.7 3.5 10.3 7.6 I Talc Talc None None Talc Talc (.1 ) ( I .0) (1 .) (1 ) None None AIBN None CE~MIC CELMI
(1.0) (335) (335) 0 . 1 5 ~ i 1 . 1 1 . 1 0 . 78 0 . 93 11~2~0 EXAMPLE 8 (Experiments No 90 to No. 103) .
Into an autoclave of 100 liter capacity made of stainless steel and e~uipped with a stirrer were introduced 30 kg of a copolymer resin composed of 90% by weight of vinyl chloride and 10% by weight of vinyl acetate and having an average degree of polymerization of 1,050 and a pore volume of 0.023 ml/g, 50 kg of purified water and 15 g of a partially saponified polyvinyl alcohol; and then 6 kg of trichlorofluoromethane and 3 kg of butane were introduced into the autoclave with pressurization followed by agitation at 70C for 8 hours to impregnate the resin with trichlorofluoromethane and butane as the volatilizable foaming agents. After completion of impregnation, cooling to room temperature and discharging of excess foarning agents, the resin was dehydrated by centrifugal separation and dried under air flow at 40 to 50C. The total amount of trichlorofluoro-methane and butane in the thus impregnated resin was 12.0% by weight.
Expandable resin compositions were prepared each by blending 100 parts of the above prepared resin impregnated with the volatilizable foaming agents, 2 parts of a tin-containing stabilizing agent and 1 part of calcium stearate along with or without the addition of 1 part of talc as the nucleating agent, 0.5 part of CELMIC 133 as the decomposable foaming agent and one of the acrylic resins E-7 to E-13 in an amount as indicated in Table 8. The resin compositions were fabricated into foamed bodies in the form of a slab by use of an extruder machine operated with the conditions as given below:
The nucleating agent was omitted in Experiments No. 100 and No. 101 and the decomposable foaming agent was omitted 30 in Experiments No. 100 and No. 102.

`F$

~1223SO

Acrylic resins:
E-7: a copolymer resin composed of 90% by weight of methyl methacrylate and 10% by weight of ethyl acrylate and having a reduced viscosity of 4.5 dl/g at 25 C, E-8: a copolymer resin composed of 90% by weight of methyl methacrylate and 10% by weight of ethyl acrylate and having a reduced viscosity of 7.0 dl/g at 25C, E-9: a copolymer resin composed of 90% by weig-ht of methyl methaerylate and 10% by weight of ethyl acrylate and having a reduced viscosity of 11.0 dl/g at 25C, E-10: a copolymer resin eomposed of 90% by weight of methyl methaerylate and 10% by weight of ethyl aerylate and having a redueed viseosity of 15.3 dl/g at 25C, E-ll: a eopolymer resin eomposed of 95% by weight of methyl methacrylate and 5% by weight of butyl aerylate and having a redueed viseosity of 10.7 dl/g at 25C, E-12: a copolymer resin eomposed of 80% by weight of methyl methaerylate, 5% by weight of ethyl aerylate, 5% by weight of butyl aerylate and 10% by weight of butyl methacrylate and having a reduced viseosity of 11.0 dl/g at 25C, and E-13: a eopolymer resin composed of 80% by weight of methyl methaerylate and 20% by weight of ethyl acrylate and having a reduced viscosity of 2.0 dl/g at 25 C.

~ - 42 -~Z;2 3SO

Operating conditions of the extruder machine:
Screw diameter 65 mm Screw length 1,950 mm Screw compression ratio 3.0 Die 100 mm width and 8 mm height Screens one with ao mesh opening and one with 100 mesh opening Cylinder temperature Cl = 95 C
C2 = 130C
C3 = 150C
Die temperature 120C
Revolutions 20 r.p.m.
The thus obtained foamed slabs were examined for bulk density, cell structure, compression strength as determined by the method specified in ASTM D 1621 and flexural strength as determined by the method specified in ISO R 1209 to give the results set out in Table 8.
In Experiments No. 98 and No. 99, premature expansion of the resin compositions took place while still in the die leading to broken foams and shrinkage of the foamed slabs after molding, with less uniform cell structure. The foamed slabs obtained in Experiments No. 102 and No. 103 were also less uniform in their cell structure although no premature expansion of the resin compositions took place.
The results given in Table 8 show that an acrylic resin with an increased reduced viscosity can give the advantages of:
the possibility of reducing the amount of the acrylic resin required, increased gas retention for forming the foams, stabilization of the foam cells and a decrease in the shrinkage ;~

23~0 of the foams. On the other hand, when the acrylic resin used has a low reduced viscosity or the amount of the acrylic resin is insufficient, the resultant foams break, shrink after molding and have a coarser cell structure.

~11223~0 Table 8 Experiment No. gn 9l 92 93 94 95 A~rylic resin E-7 (E68) (5)E-11 (6)2E(23o .
; Bulk 0.048 0.048 0.043 0.050 0.049 0.067 Proper-!cell A A A A A A
tieS Of~S~trUcture foamed I Compression slab~stren/gth2, 3.4 3.43.o 4.5 4.4 6.3 !
Flexural strength, 5.7 5.65.0 6.3 6.0 9.3 ¦ kg/cm2 Cont'd.
Table 8 Cont'd.

96 97 98 99 100 lOl l02 l03 E-10E-10 E-10 E-13 E-7 E-7 NoneNone (5)(25) (0.3) (5) (10)(10) 0.0~2 0.0500.23 0.250.12 0.095 0.16 0.-l5 3.03.6 21.0 22.3 _ _ _ 5.l6.5 29.3 30.4 _ _ _ _ .~' ~1223~0 EXAMPLE 9 (Experiments No. 104 to No. 111) Into an autoclave of 10 liter capacity made of stainless steel and equipped with a stirrer were introduced 3 kg of a homopolymerlc polyvinyl chloride resin or vinyl chloride and vinyl acetate copolymer resins whereinthe vinyl acetate resin content is given in Table 9,having an average degree of polymerization and a pore volume as indicated in Table 9, 5 kg of purified water and 1.5 g of a partially saponified polyvinyl alcohol; and then 600 g of trichlorofluoromethane and 300 g of butane were introduced into the autoclave with pressurization followed by agitation at 70C for 8 hours to impregnate the resins with trichlorofluoromethane and butane as the volatilizable foaming agents. After completion of impregnation, cooling to room temperature and discharging of excess foaming agents, the resins were dehydrated by filtration and dried under air flow at 40 to 50C for 5 hours. The total amount of the foaming agents in the thus impregnated resins were as set out in Table 9.
Expandable resin compositions were prepared each by blending 100 parts of the above obtained resins impregnated with the volatilizable foaming agents, 2 parts of a tin-containing stabilizing agent, 1 part of calcium stearate, 1 part of talc as a nucleating agent and 10 parts of one of the acrylic resins E-7, E-10 or E-13 as a foam-conditioning agent. The resin compositions were fabricated into foamed bodies in the form of a cylindrical rod in the same manner as in Example 7.
The bulk density and the cell structure of these foamed rods were as set out in Table 9. The foamed rods obtained in Experiments No. 109 and No. 110 exhibited slight shrinkage after molding.

B`

llZ23~

The results given in Table 9 show that when the vinyl chloride-based resin has an increased degree of polymerization, the use of an acrylic resin with a correspondingly increased reduced viscosity is preferable; and foamed rods of high expansion with uniform cell strueture can be obtained from a resin with a relatively redueed eontent of vinyl aeetate, whieh otherwise requires a relatively high fabrieation temperature, by suitable selection of the aerylie resin used as the foam-eonditioning agent.

~`' .~

1~223SO

I o o~ ~,_ ~ O u~ r-~ ~ O ~
,~ a: o ~ o m _ C C~
~ o ~ ~o ~1 O 0 O I r O c~
O O
_ g r-~ ,_ .
o ~ ~ ~ ~0 0 r- O
O ~_~ O
_ O O ~ _~ O
~ ~ r- t O
~ _ O ~ O
l_ O 0 O O
O O Ir~ 1~ r- _ ~O
~ a~ o ~ o o c _ O r O
_ - o ~ 1 O-` ~D ~
a~ o O O O I r O ¢
1) ~ O ~ O
D _ (~ U~ O C\J O o U~
0~ O ~ O
~_ _ O
r- o _~ ao o u~ 8 O r- O O
~ O ~ O' r . _ _ h .,, ,~ ~
a) J ~~ 1~ ~i u~ ~ ~1 3 +~ ~ ~ 0 ~ ~1 ~: ~ ~ h ~ ~ a~ ,n .,, ~h--- ~ a~ ~
a~ o ~ O ~ P~u~ m ~ b~ ~
'~:~ ~O~`o ~ ~ ~ ~

I . o ~ ~ .

B

EXAMPLE 10 (Experiments No. 112 to No. 125) Into an autoclave of 5 liter capacity made of stainless steel and equipped with a stirrer were introduced 1,000 g of a homopolymeric polyvinyl chloride resin or a copolymer resin of vinyl chloride and vinyl acetate, wherein the vinyl acetate content, average degree of polymerization and pore volume are indicated in Table 10, 2,000 g of purified water and 1.0 g of a partially saponified polyvinyl alcohol; and then 150 g of trichlorofluoromethane and 100 g of butane were introduced into the autoclave with pressurization followed by agitation at 70C for 8 hours to impregnate the resins with trichlorofluoromethane and butane as the volatilizable foaming agents. After completion of impregnation, cooling to room temperature and discharging of excess foaming agents, the resins were dehydrated by filtration and dried under air flow at 40 to 50C for about 5 hours.
The total amount of the foaming agents in the resins impregnated therewith were determined to give the results as set out in Table 10. The loss of the foaming agents by dissipation during storage at 20C for 1 week ranged from 6 to 9% for each of the resins.
Expandable resin compositions were prepared each by blending 100 parts of the above obtained resins impregnated with foaming agents, 2 parts of a tin-containing stabilizing agent and 1 part of calcium stearate along with or without the addition of a nucleating agent of the type and in an amount indicated in Table 10, a decomposable foaming agent also as given in Table 10 and a copolymer resin S-l composed of 70~ by weight of styrene and 30% by weight of acrylonitrile and having a reduced viscosity of 12.0 dl/g at 25C as a styrene-based iB

1~22350 foam-conditioning resin in an amount indicated in Table 10.
The resin compositions were fabricated into foamed bodies in the form of a cylindrical rod by extrusion molding. The operating conditions of the extruder machine were substantially the same as in Example 7.
The thus obtained foamed rods were examined for bulk density and cell structure to give the results as set out in Table 10.

~-? - 50 -3;:~

Table 10 Experiment No. 112 113 11~ 115 116 117 Content of vinyl acetate, 5 10 0 10 10 10 PVC Y ~ g~ _ . . .. ._................... .
resin 400 750 750 10001000 1000 Vp, ml/g0.011 0.013 0.060 0.025 0.025 0.025 Impre ~gnation with volatilizable foaming 11.0 10.8 7.8 9.7 9.7 9.7 agent, % by weight Nucleatin~ agent Talc Talc Talc Talc Talc ORBEN
(parts~ (2.0) (1.0) (1.0) (0.03) (0.5) (5) Decomposable None CEL~IIC None SHC CELMIC AIBN
foaming agent 133 (4.0) 133 (0.5) (parts) (1.0) (1.5) Styrene-based 6.06.0 10.08.0 8.0 8.0 resin (S-1), parts Proper-- Bulk ti es o f density, 0.060 0.044 0.061 0.049 0.050 0.055 foamed g/ml rod Cell structure A A A A A A

Cont'd.

:L1223~;i0 Table lO Cont'~.

3 - r---0-- l21 1Z~ 123 1Z4 -lo ~ 10 10 10 ~ 10 ~1 lO00 1700 11000 1000 1000 1700 2100 1800 _ .
0.025 0.02~ 0.030 0.030 0.030 0.25 0.21 0.025 . ....................................... , 9.7 9.3 9.4 9.4 9.4 2.7 3.5 6.0 _ l HAKU- Talc Talc None None None None Talc ENKA (1.0) (~ 0) _ ¦ - (1 0) ( 3) None None AIBN None None None None ¦ 8.0 lO.0 None None 8 None 8 None . _ .

jo.o60 0.069 0,Z0 ~ 0.20 1.1 ~.1 0.30 ; A A C ~ ~ C C B

23S~

EXAMPLE 11 (Experiments No. 126 to No. 135) Into an autoclave of 5 liter capacity made of stainless steel and equipped with a stirrer were introduced 1,000 g of a copolymer resin composed of 90% by weight of vinyl chloride and 10% by weight of vinyl acetate and having an average degree of polymerization of 850 and a pore volume of 0.015 ml/g, 2,000 g of purified water and 1.0 g of a partially saponified polyvinyl alcohol; and then one or two kinds of volatilizable foaming agent(s) as indicated in Table 11, was added or introduced with pressurization into the autoclave followed by agitation at 70 C for 8 hours to impregnate the resin with the foaming agent(s).
After completion of impregnation, cooling to room temperature and discharging of excess foaming agent(s), the resins were dehydrated by centrifugal separation and dried under air flow at 40 to 50C. The amount of the foaming agent(s) contained in each resin impregnated therewith was as set out in Table 11.
Expandable resin compositions were prepared each by 20 blending 100 parts of the above obtained resins impregnated with the foaming agent(s), 2 parts of a tin-containing stabilizing agent and 1 part of calcium stearate with talc as a nucleating agent, CELMIC 133 as a decomposable foaming agent and the styrene-based copolymer resin S-l as a foam-conditioning agent each in an amount as indicated in Table 11. The resin compositions were fabricated into foamed rods in the same manner as in the preceding example. The bulk density of the thus obtained foamed rods were as set out in Table 11. The : foamed rods in Experiments No. 133 and No. 134 shrank after molding.

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EXAMPLE 12 (Experiments No. 136 to No. 142) Into an autoclave of 100 liter capacity made of stainless steel and equipped with a stirrer were introduced 30 kg of a copolymer resin composed of 90% by weight of vinyl chloride and 10% by weight of vinyl acetate and having an average degree of polymerization of 1,050 and a pore volume of 0.023 ml/g, 50 kg of purified water and 15 g of a partially saponified polyvinyl alcohol, and then 6 kg of trichlorofluoromethane and 3 kg of butane were introduced into the autoclave with pressurization followed by agitation at 70C for 8 hours to impregnate the resin with trichlorofluoromethane and butane as the volatilizable foaming agents. After completion of impregnation, cooling to room temperature and discharging of excess foaming agents, the resin was dehydrated by centrifugal separation and dried under air flow at 40 to 50C. The total amount of the foaming agents in the resin impregnated therewith was 12.0~ by weight.
Expandable resin compositions were prepared each by blending 100 parts of the above obtained copolymer resin impregnated with the foaming agents, 2 parts of a tin-containing stabilizing agent, 1 part of calcium stearate, 1 part of talc as a nucleating agent, 0.5 part of CELMIC 133 as a decomposable foaming agent and one of the styrene-based copolymer resins S-2 to S-5 as described below as a foam-conditioning agent in an amount indicated in Table 12. The resin compositions were fabricated into foamed bodies in the form of a slab by extrusion molding with an extruder machine operated as in Example 8.
The thus obtained foamed slabs were examined for bulk density, cell structure, compression strength and flexural ~22~

strength to give the results as set out in Table 12. In Experiments No. 141 and No. 142, premature expansion of the resin compositions took place while still in the die leading to broken foams and shrinkage of the foamed slabs after molding.

Styrene-based copolymer resins:
S-2: a copolymer resin composed of 70% by weight of styrene and 30% by weight of acrylonitrile and having a reduced viscosity of 2.0 dl/g at 25C, S-3: a copolymer resin composed of 70% by weight of styrene and 30~ by weight of acrylonitrile and having a reduced viscosity of 4.0 dl/g at 25C, S-4: a copolymer resin composed of 70% by weight of styrene and 30% by weight of acrylonitrile and having a reduced viscosity of 10.0 dl/g at 25C, and S-5: a copolymer resin composed of 75% by weight of styrene and 25% by weight of acrylonitrile and having a reduced viscosity of 14.6 dl/g at 25C.
The results given in Table 12 show that a styrene-based copolymer resin with an increased reduced viscosity as thefoam-conditioning agent can give the advantages of: improved gas retention or foam building, stabilization of foams and reduced shrinkage even when the amount of the resin admixed is relatively small; whereas the use of a resin with a smaller reduced viscosity leads to broken foams and increased shrinkage after molding resulting in coarser cell structure, especially, when the amount of addition is insufficient.

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EXAMPLE 13 (Experiments No. 143 to No. 148) Into an autoclave of 10 liter capacity made of stain-less steel and equipped with a stirrer were introduced 3 kg of a homopolymeric polyvinyl chloride resin or a copolymer resin of vinyl chloride and vinyl acetate, wherein the content of vinyl acetate, the average degree of polymerization and pore volume were as given in Table 13, 5 kg of purified water and 1.5 g of a partially saponified polyvinyl alcohol; and then 600 g of trichlorofluoromethane and 200 g of butane were introduced into the autoclave with pressurization followed by agitation at 70C for 8 hours to impregnate the resin with trichlorofluoro-methane and butane as the volatilizable foaming agents. After completion of impregnation, cooling to room temperature and discharging of excess foaming agents, the resin was dehydrated by filtration and dried under air flow at 40 to 50C for 5 hours. The total amount of the foaming agents in the resin impregnated therewith was as given in Table 13.
Expandable resin compositions were prepared each by blending 100 parts of the above obtained resin impregnated with the volatilizable foaming agents, 2 parts of a tin-containing stabilizing agent, 1 part of calcium stearate, 1 part of talc as a nucleating agent, 0.5 part of CELMIC 133 as a decomposable foaming agent and a styrene-based resin of the type and in the amount as indicated in Table 13 as a foam-conditioning agent. The resin compositions were fabricated by extrusion molding into foamed rods in the same manner as in Example 7.
The bulk density and cell structure of these foamed rods were as set out in Table 13. The foamed rod in Experiment 147 shrank to some extent after molding and breakage of the foam took place in Experiment No. 148 resulting in shrinkage of the foamed rod after molding.

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3~0 The results given in Table 13 show that the styrene-based resin as the foam-conditioning agent should preferably have an increased reduced viscosity when the vinyl chloride-based resin has a relatively large degree of polymerization. A foamed rod of high expansion with a uniform cell structure can be obtained even with a vinyl chloride-based resin with zero or a relatively small vinyl acetate content, which otherwise requires a relatively high fabricating temperature, by suitable selection of the foam-conditioning agent.
On the other hand, a copolymer resin having a relatively low degree of polymerization can give a foamed rod of high expansion even with a styrene-based resin, as the foam-conditioning agent, having a relatively low reduced viscosity when the content of vinyl acetate in the copolymer resin is large but a foamed rod of high expansion can only be obtained with difficulty with a copolymer resin of low vinyl acetate content.

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Table 13_ ' I
Experiment No.143 14~ 145 14~ 147 148 _ .
Conten-t of vinyl acetate, 5 10 0 10 10 0 PVC ~ by weight ., .
resin P 700 1500750 800 1500 850 Vp, ml/g 0.021 0.033 0.0370.021 0.033 0.038 _ =
Im~ r egnation wi th ~`oaming agent, 11 . 5 lO . 5 lO . 1 11. 5 lO . 5 lO . O
/O by we ight Styrene-based S-5 S-5 S-5 S-3 S-3 S-2 resin (parts) (6) (10) (10)(10) (10) (10) :., Proper- Bulk 0.043 0.059 0.0550.050 0.073 o. 15 ties of density, foamed g/ml rod Cell A A A A A C
structure l l ~'

Claims (37)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A resin composition expandable into a foam by heating which comprises:
100 parts by weight of a polyvinyl chloride-based resin having an average degree of polymerization not exceeding 2,000 and a pore volume not exceeding 0.20 ml/g; and at least l part by weight of a volatilizable foaming agent selected from the group consisting of: a hydrocarbon, a halogenated hydrocarbon and mixtures thereof having a boiling point not exceeding 90°C and impregnated in said polyvinyl chloride-based resin.

2. A resin composition expandable into a foam by heating which comprises:
100 parts by weight of a polyvinyl chloride-based resin having an average degree of polymerization not exceeding 2,000 and a pore volume not exceeding 0.20 ml/g;
at least l part by weight of a volatilizable foaming agent selected from the group consisting of: a hydrocarbon, a halogenated hydrocarbon and mixtures thereof having a boiling point not exceeding 90°C and impregnated in said polyvinyl chloride-based resin; and from 0.5 to 30 parts by weight of a foam-conditioning agent selected from the group consisting of: an acrylic resin, a styrene-based resin and mixtures thereof.

3. A resin composition expandable into a foam by heating which comprises:
100 parts by weight of a polyvinyl chloride-based resin having an average degree of polymerization not exceeding 2,000 and a pore volume not exceeding 0.20 ml/g;
at least 1 part by weight of a volatilizable foaming agent selected from the group consisting of: a hydrocarbon, a halogenated hydrocarbon and mixtures thereof having a boiling point not exceeding 90°C and impregnated in said polyvinyl chloride-based resin;
from 0.5 to 30 parts by weight of a foam conditioning agent selected from the group consisting of: an acrylic resin, a styrene-based resin and mixtures thereof; and from 0.01 to 20 parts by weight of a nucleating agent.

4. The resin composition of claim 1, 2 or 3, wherein said polyvinyl chloride-based resin is a copolymer resin comprising at least 60% by weight of vinyl chloride.

5. The resin composition of claim 1, 2 or 3, wherein said polyvinyl chloride-based resin is a copolymer resin comprising up to 40% by weight of a monomer selected from the group consisting of: a vinyl ester, a vinylidene halide, a vinyl halide other than vinyl chloride, acrylic acid and an ester thereof, methacrylic acid and an ester thereof, acrylonitrile, methacrylonitrile, maleic acid, an ester and anhydride thereof, fumaric acid and an ester thereof, an olefin and mixtures thereof.

6. The resin composition of claim 1, 2 or 3, wherein said polyvinyl chloride-based resin is a copolymer resin consisting of from 60 to 97% by weight of vinyl chloride and from 40 to 3% by weight of vinyl acetate.

7. The resin composition of claim 1, 2 or 3, wherein said polyvinyl chloride-based resin has an average degree of polymerization of at least 300.

8. The resin composition of claim 1, 2 or 3, wherein said polyvinyl chloride-based resin has a pore volume not exceeding 0.10 ml/g.

9. The resin composition of claim 1, 2 or 3, wherein said volatilizable foaming agent has a boiling point not exceeding 70°C.

10. The resin composition of claim 1, 2 or 3, wherein said volatilizable foaming agent is used in an amount from 3 to 30 parts by weight, per 100 parts by weight of said polyvinyl chloride-based resin.

11. The resin composition of claim 2, wherein said foam conditioning agent has a reduced viscosity of at least 3.0 dl/g as measured in a chloroform solution of 0.1 g/100 ml concentration at 25°C.

12. The resin composition of claim 2, wherein said acrylic resin has a reduced viscosity of at least 5.0 dl/g as measured in a chloroform solution of 0.1 g/100 ml concentration at 25°C.

13. The resin composition of claim 2, 11 or 12, wherein said acrylic resin is used in an amount of 3 to 20 parts by weight per 100 parts by weight of said polyvinyl chloride-based resin.

14. The resin composition of claim 2, 11 or 12, wherein said acrylic resin is a polymethyl methacrylate.

15. The resin composition of claim 2, wherein said acrylic resin is a copolymer resin comprising methyl methacrylate and at least one acrylic ester selected from the group consisting of: an alkyl acrylate and an alkyl methacrylate other than methyl methacrylate.

16. The resin composition of claim 15, wherein the content of methyl methacrylate in said copolymer resin is in the range of 60 to 95% by weight.

17. The resin composition of claim 2, wherein said styrene-based resin is used in an amount of 3 to 20 parts by weight per 100 parts by weight of said polyvinyl chloride-based resin.

18. The resin composition of claim 2, wherein said styrene-based resin is a copolymer resin consisting of from 90 to 40% by weight of styrene and 10 to 60% by weight of a comonomer copolymerizable with styrene.

19. The resin composition of claim 18, wherein said comonomer copolymerizable with styrene is acrylonitrile.

20. The resin composition of claim 18 or 19, wherein said copolymer resin consists of styrene, acrylonitrile and an additional monomer selected from the group consisting of:
an acrylic acid ester, a methacrylic acid ester, maleic acid and an ester thereof, fumaric acid and an ester thereof and maleic anhydride.

21. The resin composition of claim 2, wherein said acrylic resin and styrene-based resin are prepared by an emulsion polymerization method.

22. The resin composition of claim 3, wherein said nucleating agent is an inorganic powdery material having an average particle diameter not exceeding 30 µm.

23. The resin composition of claim 3, wherein said nucleating agent is an inorganic powdery material having an average particle diameter not exceeding 10 µm.

24. The resin composition of claim 22 or 23, wherein said inorganic powdery material is selected from the group consisting of: calcium carbonate, talc, barium sulfate, fumed silica, titanium oxide, clay, aluminum oxide, bentonite, diatomaceous earth and mixtures thereof.

25. The resin composition of claim 3, wherein said nucleating agent is the product of the combination of an acid which is solid at room temperature and a base selected from the group consisting of: a carbonate of sodium, potassium and ammonium and a hydrogencarbonate of sodium, potassium and ammonium.

26. The resin composition of claim 25, wherein said acid which is solid at room temperature is selected from the group consisting of: citric acid, tartaric acid and oxalic acid.

27. The resin composition of claim 25, wherein said acid which is solid at room temperature is boric acid.

28. The resin composition of claim 3, which further comprises a decomposable foaming agent in an amount not exceeding 5 parts by weight per 100 parts by weight of said polyvinyl chloride-based resin.

29. The resin composition of claim 28, wherein said decomposable foaming agent is selected from the group consisting of: an azo compound, a nitroso compound, a sulfonyl hydrazide compound and sodium hydrogen carbonate.

30. The resin composition of claim 1, 2 or 3, wherein said polyvinyl chloride-based resin is produced by the suspension polymerization of monomers selected from the group consisting of: vinyl chloride monomers and a monomer mixture mainly composed of vinyl chloride monomers, in an aqueous medium containing a suspending agent and in the presence of a free radical polymerization initiator soluble in the monomer phase.

31. The resin composition of claim 1, 2 or 3, wherein auxiliary agents selected from the group consisting of: a plasticizer, a flame retardant, an anti-oxidant, an anti-static agent and mixtures thereof are further added to said resin composition.

32. An expanded foam prepared from the resin composition of claim 1, 2 or 3.

33. An expanded foam prepared from the resin composition of claim 11, 12 or 15.

34. An expanded foam prepared from the resin composition of claim 16, 17 or 18.

35. An expanded foam prepared from the resin composition of claim 19, 21 or 22.

36. An expanded foam prepared from the resin composition of claim 23, 25 or 26.

37. An expanded foam prepared from the resin composition of claim 27, 28 or 29.