JPS61278543A - Production of vinyl chloride resin foam containing inorganic particle - Google Patents

Abstract

PURPOSE:To produce the titled foam which scarcely emits smoke, little generates heat and emits lowly toxic gases during combustion, by filling an expandable compsn. consisting of a vinyl chloride resin, inorg. particles, a blowing agent and a solvent into a mold, heating it and opening the mold at a specified temp. CONSTITUTION:0.1-50pts.wt. decomposition type blowing agent (e.g. azodicarbonamide) and 0-100pts.wt. solvent (e.g. CCl4) are blended with 100pts. wt. of the combined quantity of 70-50wt% vinyl chloride resin (e.g. PVC) having an average particle size of 0.2-5mum and 30-95wt% inorg. particle (e.g. talc) having an average particle size of 0.01-300mum to obtain an expanda ble compsn. A mold is charged with the compsn., closed and heated at 50-170 deg.C under pressure to melt the vinyl chloride resin and to decompose the blowing agent. The mold is opened at a temp. of not lower than the softening point of the vinyl chloride resin to effect expansion, thus obtaining the title vinyl chloride resin foam contg. inorg. particles and having a density of 0.5-0.04g/cm<3> and an expansion ratio of 5-50.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a vinyl chloride resin foam containing inorganic particles. More specifically, the present invention relates to a method for easily and inexpensively producing the vinyl chloride resin foam, which contains a large amount of inorganic particles and has low heat generation B during combustion, low ffff1° toxicity, and low gas toxicity.

[Prior Art] Conventionally, polyvinyl chloride resin (hereinafter referred to as PVC) foams have been manufactured using, for example, a composition consisting of PVC, a blowing agent, a stabilizer, etc., as it is, or a preformed product such as an O-ru sheet. The foam is filled into a closed mold and heated under pressure, then the mold is cooled to near room temperature while still under pressure, the contents (primary foam) are taken out, and reheated with hot air or hot water. In the so-called high-pressure two-stage process, a composition consisting of PVC, a decomposable blowing agent, an isocyanate, an acid anhydride, etc. is made into a primary foam in the same manner as in the high-pressure two-stage process, and then foamed with hot water or A so-called crosslinking method in which secondary foaming is achieved by reheating with steam and causing a three-way crosslinking reaction between isocyanate, acid anhydride, and water ■A composition consisting of PVC, an acrylic processability improver, a nucleating agent, etc. is supplied to an extruder, and an evaporative foaming agent is press-fitted into the composition heated and melted in the extruder to cause foaming.
There is the so-called extrusion method, and the so-called ethostomer method, in which a gas-absorbing plastisol in which an inert gas such as carbon dioxide gas is mechanically stirred and absorbed into PvC plastisol under cooling and pressure is foamed by heating with high frequency or the like.

However, if a large amount of inorganic particles are included in a foam, moldability becomes extremely poor, so it is difficult to economically obtain a good foam using either method. .

For example, as an application of the high-pressure two-stage method,
No. 76 and Japanese Patent Publication No. 53-7944 disclose a method for producing a PVC foam containing a large amount of inorganic particles.

However, in these methods, the mold is cooled and the primary foam is taken out according to the procedure of the normal high-pressure two-stage method, and then reheated to perform the secondary foaming. There is a humidity distribution in which the temperature near the surface is high and the temperature gradually decreases toward the center.As a result, there is a difference in the foaming speed near the surface and the center, causing shrinkage and deformation of the foam, or extreme In such cases, delamination may occur in the foam, which may even grow into large cavities. Although the secondary foaming due to reheating progresses gradually, the time required for foaming is long, and by the time foaming is completed, the rate of foaming gas escaping to the outside of the foam increases, reducing the efficiency of the blowing agent. As the density decreases, the apparent density of the foam increases. Furthermore, in order to cool the primary foam to near room temperature, a large amount of cooling medium is required, and the mold and press pressure plate become cold, which means that energy is used for heating for the next production cycle. The amount also increases. This also means that it takes time to cool down the mold and raise the temperature, which lengthens the production cycle and reduces productivity. Moreover, the amount of heat required for secondary foaming is considerable.

Further, in these methods, butane is used as a blowing agent, but since butane has a high gas permeation rate to the PvC/solvent system, its efficiency as a blowing agent is low, and highly foamed products are not suitable for manufacturing.

Furthermore, in these methods, when kneading raw materials to produce a foamable composition (sol), there is a problem that special measures are required, such as separating the kneading in two steps or kneading under heating. There is also.

In this way, the Publication of Special Publication No. 52-267764 and the Publication of Special Publication No. 52-267764,
The method disclosed in Publication No. 34944@ has drawbacks in terms of product quality, productivity, and economy.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned circumstances, and when producing a foam from a PvC foamable composition containing a large amount of inorganic particles, This was done in order to solve problems such as poor productivity and economy caused by this method, and defects in the quality of the resulting foam.

[Means for Solving the Problems] The present invention is characterized in that a foamable composition obtained by kneading PVC, inorganic particles, a decomposable blowing agent, a solvent, and a stabilizer all at once at room temperature is filled into a closed vine mold. The above drawbacks are solved by heating under pressure, opening the mold at a temperature higher than the softening temperature of PvC in the foamable composition, and simultaneously causing foaming.

Here, the softening temperature is defined by the foaming power of the blowing agent, and the foaming ratio that has practical significance (it varies depending on the application, but for example, when used as a building insulation material, the apparent density is approximately 0.15 a/cal or less). This is the temperature at which the resin film stretches until the foaming ratio is reached, which is higher than room temperature.

That is, in the present invention, the mold is opened at a temperature higher than the softening temperature of PvC, and the foaming force of the foaming agent contained in the molded object is used to cause foaming to occur from deep within the molded object, eliminating the need for secondary foaming. In addition, since the mold and press pressure plate do not need to be completely cooled, the cooling time is shortened, which reduces the amount of energy used to reheat them during the production of stubs, and shortens the temperature rise time. Regarding the method for producing PvC foam containing inorganic particles, the resulting foam contains a large amount of inorganic particles, so it has the characteristics of low calorific value, low smoke emission, and low gas toxicity when burned. It is something that you have.

Further, in the present invention, it is preferable to use nitrogen gas generated from a decomposable blowing agent as the blowing agent.

Nitrogen gas has a very low gas permeation rate with respect to the PvC solvent system, so it is highly efficient as a blowing agent, and has the characteristics that a highly foamed product with a good appearance can be easily obtained.

Furthermore, in the present invention, when kneading the raw materials to prepare the foamable composition, no special measures are required, and it is sufficient to simply knead them all at once at room temperature and normal pressure using a normal mixing device. It also has the following characteristics.

[Example] As PvC used in the present invention, polyvinyl chloride alone or polyvinyl chloride-vinyl acetate copolymer, chlorinated polyvinyl chloride, thermoplastic polyurethane, acrylonitrile-butadiene copolymer (NBR), chlorinated polyethylene , methacrylic ester-acrylic ester copolymer, ethylene-vinyl acetate copolymer, vinyl chloride-
A mixture of polyvinyl chloride and at least one resin that is compatible with polyvinyl chloride, such as a vinylidene chloride copolymer, and a mixture in which the polyvinyl chloride in the mixture is 50% by weight or more. .

The polyvinyl chloride is called paste resin, and has an average particle size of, for example, 0.2 to 5 mm, preferably 0.5 to 2 mm.
0- ones are particularly suitable.

When this paste resin is mixed with another resin, it is preferable that the paste resin is contained in an amount of 50% by weight or more.

The inorganic particles used in the present invention have an average particle size of 0.01 to
There is no particular restriction as long as the particle size is about 300 mm, but from the viewpoint of price and availability, hollow particles such as calcium carbonate, talc, aluminum hydroxide, magnesium hydroxide, asbestos, rock wool, or shirasu balloons are preferred. These are preferably used alone or in combination. When these inorganic particles are treated with a coupling agent such as silane, titanate, or fatty acid, PvC
It is preferable because it has good affinity with. The ratio of PVC/inorganic particles to be used is selected at a weight ratio of 70/30 to 5/95, preferably 50/50 to 10/90, and more preferably 40/60 to 20/80.

Examples of the blowing agent used in the present invention include decomposable blowing agents.

Examples of the decomposable blowing agent include azodicarbonamide, azohisisobutyronitrile, diazoaminobenzene, N,N-dinitrosopentamethylenetetramine,
Examples include D-toluenesulfonyl hydrazide.

The use υ of the blowing agent varies depending on the desired expansion ratio and the type of blowing agent, but usually the total amount of PvC and inorganic particles is 1
It is preferable to use 0.1 to 50 parts, preferably 1 to 30 parts. Note that it may be used in combination with a foaming aid.

Solvents used in the present invention include esters such as isoamyl formate and n-butyl acetate, polyhydric alcohol derivatives such as ethyl cellosolve and ethyl cellosolve acetate,
Ketones such as diisobutyl ketone and methyl isobutyl ketone, aromatic hydrocarbons such as toluene, xylene, and ethylbenzene, halogenated hydrocarbons such as phosphorus, carbon tetrachloride, carbonic acid derivatives such as diethyl carbonate, and phosphorus compounds such as tricresyl phosphate. etc., and may be used alone or in combination of two or more. The amount of the solvent used is usually 0 to 100 parts, preferably 10 to 70 parts, based on 100 parts of the total Ji of PVC and inorganic particles.

In the present invention, it goes without saying that plasticizers, stabilizers, pigments, etc. may be used as necessary.

Next, the present invention will be explained in detail.

A foamable composition is prepared by blending each raw material in a predetermined amount and mixing thoroughly using a ribbon blender, a double-arm kneader, a pressurized kneader, a Banbury mixer, or the like.

The prepared foamable composition is filled into a closed mold made of aluminum alloy or the like, and the mold is set in a hydraulically driven heating press to heat the composition under pressure.

The pressure and heating conditions vary depending on the content of the composition, but PvC
It is necessary to substantially complete the melting of the foaming agent and the decomposition of the decomposable foaming agent.
The pressure is selected, and then, while the mold is kept pressurized, the temperature of the pressing plate of the press is lowered to a temperature suitable for foaming using a cooling medium such as water.

The suitable temperature for foaming varies depending on the composition, but it is lower than the above-mentioned pressurizing and heating temperature (and above the softening temperature of PvC, and a temperature of PvC that does not cause foaming gas to escape due to cell membrane rupture during foaming). It is necessary that the temperature provides a melt viscosity, for example, about 50 to 170°C.

When the mold temperature drops to a predetermined foaming temperature, the mold is opened and the contents of the mold are released to atmospheric pressure. Since the mold contents have the foaming power of the foaming agent and the PvC is above the softening temperature, the mold contents expand and foaming is completed in a short time.

According to the production method of the present invention, a desired foam can be easily produced by only secondary foaming, but secondary heating of the primary foam obtained by the production method of the present invention may also be used as an auxiliary method.

The foam thus obtained has an expansion ratio of about 5 to 50 times, and a density of 0.5 to 0.04 Q/cm3, depending on the size of the inorganic particles contained in the foamable composition. It is of a certain degree.

Next, the manufacturing method of the present invention will be explained based on Examples, but the present invention is not limited to these Examples.

Examples 1 to 18 The raw materials shown in Table 1 were blended in the proportions shown in Tables 2 to 4 so that the total amount was 500 g, and a closed double-arm kneader with an effective capacity of 172 cm was used. The mixture was kneaded for 45 minutes. During this time, cold water was passed through the kneader jacket to maintain the temperature of the composition in the range of 15 to 20°C. After mixing, the composition is allowed to flow down by gravity, and the capacity size is 170x 90x.
The mixture was filled into a 15 mm aluminum alloy mold, the mold was covered with an aluminum plate, set in a hydraulically driven heating press, and heated from room temperature to 115° C. in 10 minutes. The clamping pressure of the press was approximately 250 k (l) per 1 cm2 of mold area. After holding the mold at 175°C for 35 minutes, cold water was passed through the cooling plate of the press to bring the mold temperature to the foaming temperature in approximately 10 minutes. The temperature was lowered and kept at the foaming temperature for 10 minutes.Then, when the clamping pressure of the press was released, the contents of the mold were reduced to about 1.
Foaming was completed in seconds.

The resulting foam was visually inspected for appearance and cell uniformity on a cut surface, and its apparent density, expansion ratio, closed cell ratio, and blowing agent efficiency were measured by the following methods. The results are shown in Tables 2 to 4.

(Apparent density) Cut out a 20m+a square cube from the molded product, measure the volume and spray amount, and calculate @base/volume.

(Foaming ratio) Calculated by dividing the density of the solid content (PVC ten inorganic particles) in the foamable composition by the apparent density of the foam.

(Closed cell ratio) Measured using an air comparison hydrometer manufactured by Toshiba Beckman ■ based on the ASTH02856C method.

(Blowing agent efficiency) Calculated using the following definition formula.

The solid content in the foam is x (g) or x (Ml), the solvent in the foam is V ((1) or Y (IIi), the theoretical amount of gas generated is Zt (all), and the effective amount that contributed to foaming is Gas amount by Z
If a(d), then the theory of foam W! a T-x/(X+Y+7t) Actual density of foam A=x/(X+Y+Za) From this, blowing agent efficiency v=Za/Zt=(--x-y)/(--X-Y
) A T ×100 Comparative Example 1 After holding at 175°C for 35 minutes using a heating press, it was cooled to 25°C over 30 minutes. Next, a primary foam was obtained using the same raw materials and processing conditions as in Example 18, except that the press clamping pressure was released, the mold was opened, and the contents (primary foam) were taken out.

The primary foam is heated in an oven at 90℃ using hot air for about 60℃.
When the foam was reheated for a minute, the foaming rate was slow and gradually foamed, resulting in a foam with a high apparent density and low blowing agent efficiency.

The results are shown in Table 4.

Comparative Example '2 Hoga using butane as the blowing agent was prepared in the same manner as in Example 1.
After holding at 175°C for 35 minutes, it was cooled to 20'C over 45 minutes. When the primary foam taken out from the mold was reheated for about 30 minutes using hot air in an oven at 100°C, large cavities were generated in the core of the foam.

The results are shown in Table 4.

Comparative Example 3 After processing the same composition as in Example 1 under the same conditions as in Example 1, the press tightening pressure was released at a foaming temperature of 20°C. Although a foam with good appearance was obtained, it was a low-foaming product with a foaming ratio of 2 times.

The results are shown in Table 4.

[Effects of the Invention] According to the manufacturing method of the present invention, the mold is opened at a temperature higher than the softening temperature of PVC, and the foaming force of the foaming agent contained in the molded product is used to cause foaming from deep inside the molded product. In addition to eliminating the need for secondary foaming, the cooling time is shortened because the mold and press pressure plate do not have to be completely cooled, and the amount of energy used to reheat them during the production of tsutsugi is reduced. Since the heating time is short, the productivity is good, and since it can be produced economically and contains a large amount of inorganic particles, it has the effect of having a small amount of heat generated during combustion, the amount of smoke produced, and the toxicity of the generated gas.

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Claims (1)

[Scope of Claims] 1. A foamable composition obtained by kneading a vinyl chloride resin, inorganic particles, a blowing agent, and a solvent all at once at room temperature is filled into a sealable mold and heated under pressure to produce vinyl chloride. An inorganic particle-containing method characterized by melting the resin and decomposing the decomposable blowing agent, and then simultaneously opening the mold at a temperature higher than the softening temperature of the vinyl chloride resin in the foamable composition and causing foaming. A method for producing vinyl chloride resin foam. 2 Vinyl chloride resin is polyvinyl chloride alone or polyvinyl chloride-vinyl acetate copolymer, chlorinated polyvinyl chloride, thermoplastic polyurethane, acrylonitrile-butadiene copolymer (NBR), chlorinated polyethylene, methacrylate ester-acrylic It is a mixture with at least one resin that is compatible with polyvinyl chloride, such as acid ester copolymer, ethylene-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, and the polyvinyl chloride in the mixture The method for producing a vinyl chloride resin foam containing inorganic particles according to claim 1, wherein the amount is 50% by weight or more. 3. The method for producing a vinyl chloride resin foam containing inorganic particles according to claim 1, wherein the inorganic particles are treated with a titanate-based, silane-based, or other coupling agent. 4. The method for producing an inorganic particle-containing vinyl chloride resin foam according to claim 1, wherein the blowing agent is a decomposable blowing agent that is decomposed by heating and generates nitrogen gas. 5 The solvent is esters such as isoamyl formate and n-butyl acetate, polyhydric alcohol derivatives such as ethyl cellosolve and ethyl cellosolve acetate, ketones such as diisobutyl ketone, aromatic hydrocarbons such as toluene, xylene, and ethylbenzene, chlorobenzene, carbon tetrachloride, etc. The method for producing a vinyl chloride resin foam containing inorganic particles according to claim 1, which is a halogenated hydrocarbon, a carbonic acid derivative such as diethyl carbonate, a phosphorus compound such as tricresyl phosphate, or a mixture thereof. .