Improvements in neither toxic nor environmentally noxious foamed-polymer products

Abstract: A cellular, foamed-polymer product is disclosed, which is constituted by a mixture comprising: at least one isocyanate, at least one anhydride, at least one vinylidene compound, poly-(vinyl chloride), at least one foaming agent, a heat stabilizer, calcium stearate and zinc stearate. The product production scraps and processing wastes and residues are not riskful for health and environment, and can be disposed of as "waste similar to solid municipal waste".

Description: The present invention relates to cellular, foamed polymer products based on poly(vinyl chloride). Cellular foamed products based on poly(vinyl chloride) are for example known from NL-A-135779 and EP-A-74907. NL-A-135779 teaches the use of toluene-diisocyanate and azobis-isobutyronitril as foaming agent. EP-A-74907 concerns a process to realize a cellular foamed product based on poly(vinyl chloride) comprising the following steps: a. To extrude a preform from a mixing composed by: poly(vinyl chloride) a blowing agent an organic anhydride; b. to cut the obtained preform in the desired blank; c. to expand the blank obtained in water at a temperature above 70°C. More particularly, the present invention relates to cellular, foamed-polymer products based on poly(vinyl chloride), in which the production scraps, the processing wastes and residues and the composites fabricated by using said cellular foamed polymer, when have become no longer useable, can be disposed as "waste similar to solid municipal waste", therefore with no risks for health or environment. The presently known product is constituted by a mixture of one or more isocyanates, such as toluene-diisocyanate and/or polymethylene-polyphenylisocyanate, poly(vinyl chloride), one or more anhydrides, such as maleic anhydride and/or phthalic anhydride, one or more vinylidene compounds, such as styrene and acrylonitrile, a foaming agent, such as azobis(isobutyronitrile), one or more heat stabilizer compounds, such as tribasic lead sulfate, dibasic lead phosphite, dibasic lead phthalate or barium-cadmium-zinc, lead-barium complexes. Said mixture, of thick consistency, after being compounded in a dissolver, is cast into a mould, and the temperature is then increased under pressure, until the temperature of 180°C is reached, in order to cause the gelation of poly(vinyl chloride) to take place. The semi-foamed article obtained, i.e., the "embryo", will complete its foaming by being heated in the presence of water or steam. The resulting cellular product may not be disposed of as a "solid municipal waste", because it contains inorganic compounds, such as tribasic lead sulfate, dibasic lead phosphite, organic compounds of metals, such as dibasic lead phthalate and barium-cadmium-zinc, lead-barium complexes, which are toxic and noxious. The general purpose of the present invention is of providing a foamed-polymer product based on poly(vinyl chloride) in which the production scraps, the processing wastes and residues and the composites fabricated by using said cellular foamed product, when no longer useable, can be disposed of as "waste similar to solid municipal waste", therefore with no risks for health and environment. Another purpose of the invention is to obtain a foamed product provided with very small cells, with a fine, regular cell texture. These purposes are achieved according to the present invention by the products disclosed in the following specification and claimed in the appended claims. In a first form of practical embodiment thereof, the cellular foamed product manufactured according to the present invention is constituted by a mixture comprising one or more isocyanates, such as 2,4/2,6-toluene-diisocyanate and/or 4,4'-diphenylmethane-diisocyanate, one or more anhydrides, such as maleic anhydride and/or phthalic anhydride, poly(vinyl chloride), two foaming agents which are azobis-(isobutyronitrile) and azodicarbonamide, and a heat stabilizer, composed of calcium stearate and zinc stearate and optionally a mixture of beta-diacetones, the main component of which is stearoyl-benzoyl-methane (available on the market under the trade name "Rhodiastab 50"). After the compound mixing step, the resulting compound, now because of thick consistency, is cast into a mould, is progressively heated, under pressure, until the maximum temperature of 165°C is reached, in order to cause the gelation of poly(vinyl chloride) to occur. After cooling, the resulting embryo is foamed, by causing the isocyanates and anhydrides to react with water, until the desired bulk density is obtained. The resulting cellular foamed article displays extremely good mechanical and chemical characteristics and temperature resistance, and its production scraps and processing wastes and residues can be disposed of as "waste similar to solid municipal waste". Example 1 A paste-like compound composed by a mixture of: from 1 % to 28% of 4,4'-diphenylmethane-diisocyanate ; from 1 % to 30% of 2,4/2,6-toluene-diisocyanate; from 3 % to 12% of maleic anhydride; from 48 % to 55% of poly(vinyl chloride); from 3 % to 14% of phthalic anhydride; from 1 % to 10% of azobis-(isobutyronitrile); from 0.02% to 4% of azodicarbonamide; and from 0.2 % to 3% of the mixture consisting of Rhodiastab 50, calcium stearate and zinc stearate; wherein the percentage by weight of each individual component is referred to the total weight of the mixture. Said compound is mixed in the dissolver, is poured into the mould and poly(vinyl chloride) is caused to undergo gelation at a maximal temperature of 185°C under pressure. On cooling, the embryo is obtained which, after being foamed in water or in the presence of steam (at the temperature of 98°C), yields a cellular foamed article with a bulk density of 30 kg/m 3 , a heat distorsion temperature of 100°C, a compression strength of (2.7 kg/cm 2 ) 264.78 · 10 3 Pa at room temperature, a styrene absorption, after total-article dipping, of 6% by weight, relatively to the weight of the tested sample, with a fine, regular cell texture. Example 2 A paste-like compound composed by a mixture of: from 45 % to 55 % of poly(vinyl chloride); from 5 % to 15 % of phthalic anhydride; from 15 % to 30 % of 2,4/2,6-toluene-diisocyanate; from 0.2% to 3 % of azodicarbonamide; from 0.2% to 3 % of azobis-(isobutyronitrile); from 0.2% to 2.5% of the mixture consisting of Rhodiastab 50, calcium stearate and zinc stearate; from 2 % to 5 % of plasticizer based on phosphate or phthalate; and from 0.1% to 0.5% of alpha-phenyl-indole; wherein the percentage by weight of each individual component is referred to the total weight of the mixture. According to the manufacturing process disclosed in Example 2, said mixture will yield a cellular foamed article having a bulk density of 80 kg/m 3 , a heat distorsion temperature, under bending stress, of 90°C, a styrene absorption, after a 2-hour total-article dipping time, of 7% by weight, relatively to the weight of the tested sample, good elastic properties, constant use temperature of 70°C. Example 3 A paste-like compound composed by a mixture of: from 5 % to 30% of 2,4/2,6-toluene-diisocyanate ; from 1 % to 30% of 4,4'-diphenylmethane-diisocyanate ; from 3 % to 17% of phthalic anhydride; from 1 % to 7% of azobis-(isobutyronitrile); from 0.5% to 5% of azodicarbonamide; from 0.5% to 2% of the mixture consisting of Rhodiastab 50, calcium stearate and zinc stearate; and from 40 % to 60% of poly(vinyl chloride) ; wherein the percentage by weight of each individual component is referred to the total weight of the mixture. According to the manufacturing process disclosed in Example 2, said mixture will yield a cellular foamed article having values of bulk density of 60 kg/m 3 , heat distorsion temperature, under bending stress, of 90°C, styrene absorption, after a 2-hour total-article dipping time, of 7% by weight, relatively to the weight of the tested sample, good elastic properties, constant use temperature of 70°C.

Claims: A cellular polymer product obtainable by mixing and foaming a composition comprising at least one isocyanate, at least one anhydride, poly(vinyl chloride), a heat stabilizer for poly(vinyl chloride) composed of calcium stearate, zinc stearate and optionally a mixture of beta-diacetones, and two foaming agents which are 2,2'-azobisisobutyronitrile and azodicarbonamide. Product according to claim 1, characterized in that said mixture comprises: from 1 % to 28% of 4,4'-diphenylmethane-diisocyanate; from 1 % to 30% of 2,4/2,6-toluene-diisocyanate; from 3 % to 12% of maleic anhydride ; from 48 % to 55% of poly(vinyl chloride) ; from 3 % to 14% of phthalic anhydride; from 1 % to 10% of azobis-(isobutyronitrile) ; from 0.02% to 4% of azodicarbonamide; from 0.2 % to 3% of the mixture consisting of stearoyl-benzoyl-methane, calcium stearate and zinc stearate. Product according to claim 1, characterized in that said mixture comprises: from 45 % to 55 % of poly(vinyl chloride) ; from 5 % to 15 % of phthalic anhydride; from 15 % to 30 % of 2,4/2,6-toluene-diisocyanate ; from 0.2% to 3 % of azodicarbonamide; from 0.2% to 3 % of azobis-(isobutyronitrile); from 0.2% to 2.5% of the mixture consisting of stearoyl-benzoyl-methane, calcium stearate and zinc stearate; from 2 % to 5 % of plasticizer based on phosphate or phthalate; and from 0.1% to 0.5% of alpha-phenyl-indole. Product according to claim 1, characterized in that said mixture comprises: from 5 % to 30% of 2,4/2,6-toluene-diisocyanate ; from 1 % to 30% of 4,4'-diphenylmethane-diisocyanate ; from 3 % to 17% of phthalic anhydride; from 1 % to 7% of azobis-(isobutyronitrile); from 0.5% to 5% of azodicarbonamide; from 0.5% to 2% of the mixture consisting of stearoyl-benzoyl-methane, calcium stearate and zinc stearate; and from 40 % to 60% of poly(vinyl chloride). Product according to claim 1, characterized in that as the heat stabilizer, in the cellular foamed material based on poly(vinyl chloride), a mixture is used constituted by calcium stearate, zinc stearate and beta-diacetones, wherein the main component is stearoyl-benzoyl-methane, having the formula

Inventors: LAURI LEONE, LAURI, LEONE
Applicants: POLIMEX S P A, POLIMEX S.P.A.
Application year: 1992
Main classification: C08J9
IPC codes: C08K3, C08K5, C08J9, C08L27, C08G18, C08G101