JPS621972B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to flame-retardant thermoplastic resin particles and a method for producing the same.

More specifically, the present invention provides primary foam particles that are flame retardant, have excellent weather resistance, oil resistance, and solvent resistance, and can obtain low specific gravity particles without using plasticizers. An object of the present invention is to provide expandable and flame-retardant thermoplastic resin particles that have good fusion properties between the primary foamed particles and can yield a foam molded product of any shape when molded in a mold. It is something to do.

Molded bodies made of thermoplastic resin, particularly foamed molded bodies, are used as heat insulating materials or heat retaining materials. In particular, products made from foamable thermoplastic resin particles impregnated with a foaming agent can be used to form any desired foam molded product, making them suitable for use in food transportation containers, flooring materials in buildings, and heat/cold insulation for tanks. It is widely used. However, a foamed molded article made of thermoplastic resin is more likely to catch fire and burn when exposed to static electricity or flame than a non-foamed molded article. For this reason, it is desired to provide flame retardant or self-extinguishing properties to foamed molded articles. For this reason, research is being widely conducted to obtain flame-retardant foam molded articles by adding flame retardants to thermoplastic resins.

Flame-retardant thermoplastic resin particles that are low specific gravity, self-extinguishing, and can be foamed by adding a flame retardant and a foaming agent to particulate polystyrene resin as a raw material for obtaining foamed molded products of any shape. It has been known. However, the foam molded products obtained by foam molding using this material had the disadvantage of being inferior in weather resistance, chemical resistance, and oil resistance.

On the other hand, foamed molded products made of vinyl chloride resin are known as flame retardant, and have excellent chemical and oil resistance. These vinyl chloride resin foams are currently manufactured by methods such as press foaming, but the reality is that no method has yet emerged for filling expandable particles into a mold to form a foam molded product. This is because even though it is possible to foam vinyl chloride resin, it is difficult to fuse the vinyl chloride resins to each other when hot molding, so it is not possible to form a molded product.

However, instead of performing this fusion by thermoforming, it is known to form a molded article by coating the surface of the resin with an adhesive or a thermoplastic resin that can be heat-fused.

However, the processing temperature of vinyl chloride homopolymer is about 160°C, and foam molding requires a very high temperature, making it difficult to mold at the usual temperature of about 100°C. The foamed molded product made of vinyl chloride polymer contains plasticizer and the like, and is not sanitary.

As a result of intensive research in order to solve the above problems, the inventors of this invention used vinyl chloride polymer or vinyl chloride copolymer as core resin particles,
By substantially absorbing a vinyl aromatic monomer into the particles and polymerizing the monomer in the particles, the resulting particles can be imparted with flame retardancy, weather resistance, oil resistance, and solvent resistance. In addition, when impregnated with a foaming agent, primary foamed particles with low specific gravity can be obtained without using a plasticizer, etc., and when molding using these primary foamed particles in a mold, each primary foamed particle is This invention was completed based on the discovery that expandable particles having good particle fusion properties and which can be made into foamed molded articles of arbitrary shapes can be obtained.

That is, the present invention comprises 50 to 80% by weight of core resin particles made of a vinyl chloride polymer and 50 to 20% by weight of a vinyl aromatic polymer polymerized with a vinyl aromatic monomer substantially absorbed into the particles. foamable flame-retardant thermoplastic resin particles consisting of flame-retardant thermoplastic resin particles containing a gaseous or liquid blowing agent at room temperature; and a core material consisting of a vinyl chloride polymer. 50 to 80 parts by weight of resin particles are suspended in an aqueous medium, 50 to 20 parts by weight of a vinyl aromatic monomer is added to the suspension and substantially absorbed by the particles, and polymerized in the presence of a polymerization catalyst. A method for producing flame-retardant thermoplastic resin particles, which comprises adding a gaseous or liquid blowing agent at room temperature before, during, or after polymerization to obtain expandable particles containing a blowing agent. It provides:

In this invention, it is necessary to use vinyl chloride polymer as the core resin particles and to polymerize the vinyl aromatic monomer in the particles. If a vinyl chloride polymer and a vinyl aromatic polymer are simply mixed together, if this mixture is molded using a normal extruder, injection molding machine, etc., the resulting molded product will contain a layer of vinyl chloride polymer and a vinyl aromatic polymer. A usable molded product cannot be obtained by separating the group polymer layer, and when a blowing agent is added to this mixture, satisfactory expandable particles cannot be obtained.

As the vinyl chloride polymer of the core material resin, a vinyl chloride homopolymer or a vinyl chloride copolymer is used. Examples of vinyl chloride copolymers include copolymers of vinyl chloride and monomers such as styrene, methyl methacrylate, methyl acrylate, vinylidene chloride, ethylene, diethyl maleate, and vinyl acetate.

When the particles of the present invention are obtained using a vinyl chloride polymer or a vinyl chloride copolymer as a core resin particle,
Since the impact resistance is poor, in order to improve this impact resistance, a polyolefin polymer may be mixed in advance with the vinyl chloride polymer or vinyl chloride copolymer. When using such a polymer,
This is preferable because a part of the vinyl aromatic monomer is graft-polymerized to this polymer, resulting in a more uniform mixture.

Examples of such polyolefin polymers include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, chlorosulfonated polyethylene, chloroprene, polybutene, etc., and one type or a mixture of two or more of these can be used. . Polyethylene and ethylene-vinyl acetate copolymer are preferably used. The amount of polyolefin polymer used is 30% as core material resin particles.
% by weight or less. If it exceeds 30% by weight, flame retardancy will be impaired, which is not preferable.

In this invention, in order to quickly absorb the vinyl aromatic monomer added, a particulate core resin is used. Particle size is 0.5
Spherical, flat or pellet-shaped particles having a diameter of ~10 mm are suitable.

In order to obtain the flame-retardant thermoplastic resin particles of the present invention, a vinyl aromatic monomer is absorbed into the core resin particles. Examples of such vinyl aromatic monomers include styrene, α-methylstyrene, ethylstyrene, vinyltoluene, vinylxylene, isopropylxylene, etc. alone or a mixture of two or more of them; % or more of a vinyl aromatic monomer and a copolymerizable monomer such as acrylonitrile, methyl methacrylate, methyl acrylate, etc.

The vinyl aromatic monomer is used so that the resulting flame-retardant thermoplastic resin particles have a composition of 50 to 20% by weight of vinyl aromatic polymer and 50 to 80% by weight of core resin.

The vinyl aromatic monomer absorbed into the core resin particles is polymerized in the particles to obtain thermoplastic resin particles that serve as the base of the expandable particles of the present invention.

If the amount of the core resin is less than 50% by weight, the properties inherent to the vinyl chloride resin will be lost, and if it exceeds 80% by weight, the foamability will deteriorate, which is not preferred.

To explain in more detail the method for obtaining flame-retardant thermoplastic resin particles of the present invention, first, core resin particles are prepared. In the case of particles of vinyl chloride homopolymer or vinyl chloride copolymer, they are used as they are as the core resin. When using a resin mixture of a vinyl chloride polymer and a polyolefin polymer, for example, they are thoroughly mixed and then fed to an extruder, where the resins are melted and uniformly kneaded. After kneading, the mixture is extruded into a large number of thin bodies through a die attached to the tip of the extruder, cooled by passing through a water tank, and cut into particles using a beletizer or the like.

The core resin particles obtained as described above are suspended in an aqueous medium containing a dispersant. Examples of the dispersant include organic compounds such as partially saponified polyvinyl alcohol, polyacrylate, polyvinylpyrrolidone, carboxymethylcellulose, methylcellulose, calcium stearate, and ethylene bisstearamide, as well as calcium pyrophosphate, calcium phosphate, calcium carbonate, and carbonic acid. Inorganic compounds made of fine powder that are poorly soluble in water, such as magnesium, magnesium phosphate, magnesium pyrophosphate, and magnesium oxide, are used. These dispersants are generally added in an amount of 0.01 to 5% by weight based on water.

Next, a vinyl aromatic monomer and a polymerization catalyst are added to the suspension in which the core resin particles are dispersed.

Examples of such polymerization catalysts include organic peroxides such as benzoyl peroxide, tert-butyl barbenzoate, lauroyl peroxide, tert-butyl peroxy-2-ethylhexanate, and tert-butyl peroxide, and azobisisobutyronitrile. , azo compounds such as azobisdimethylpaleronitrile, and the like. These catalysts are 1
It can be used as a species or as a mixture of two or more species. These polymerization catalysts can be used by being dissolved in the above-mentioned vinyl aromatic monomer or in a solvent such as benzene, toluene, xylene, etc. that does not inhibit polymerization.

In order to prevent the formation of a homopolymer of the vinyl aromatic monomer and to prevent polymerization on the surface of the core resin particles, it is desirable to gradually add the vinyl aromatic monomer little by little to the suspension.

The vinyl aromatic monomer dropped into the suspension is quickly absorbed into the core resin particles, and polymerization occurs in the core resin particles, resulting in thermoplasticity forming the base of the expandable particles of the present invention. Resin particles are obtained.

If the absorption of the monomer core resin is incomplete,
When the particles are pre-foamed into expandable particles, they become foamed (dumpling-like) with a core and non-uniform outer shape.
On the other hand, when absorption is substantially complete, pre-expanded particles are coreless and have an excellent particle shape.

The thermoplastic resin particles themselves are flame retardant and have a good ability to retain the foaming agent inside, and when made foamable, each particle is well fused during foam molding, so it is possible to It is possible to obtain a foamed molded product having the shape of , and it also has excellent rigidity. Also,
Since no flame retardant is used, deterioration in weather resistance can be minimized (in general, weather resistance is significantly reduced by mixing flame retardants).

In this invention, zinc stearate, zinc ricinol, calcium stearate,
One or more of calcium laurate, tin stearate, tin maleate, tin laurate, dibutyltin laurate, zinc stearate, dibasic lead stearate, lead naphthenate, or the like can be added in combination. Such a stabilizer has an amount of 0.05 to 6
Preferably, weight percentages are used. If it is less than 0.05% by weight, the stability effect will be poor, and if it exceeds 6% by weight, the physical properties will be poor. Further, a spreading agent such as polybutene may be used to improve the kneading of the vinyl chloride resin and the thermoplastic resin. Such a spreading agent is used in an amount of 0.1 to 3.0% by weight based on the vinyl chloride resin. Other colorants, antistatic agents, etc. can be used as appropriate.

A blowing agent is added to make the thermoplastic resin particles foamable. As the foaming agent, one that is gaseous or liquid at room temperature is used. Such blowing agents include propane, n-butane, i-
Aliphatic hydrocarbons such as butane, n-pentane, i-pentane, n-hexane, cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane, methyl chloride, ethyl chloride, dichlorodifluoromethane, chlorodifluoromethane, trichlorofluoromethane Examples include halogenated hydrocarbons such as. These blowing agents are generally contained in a proportion of 3 to 40% by weight based on the base thermoplastic resin particles.

In order to incorporate the above-mentioned blowing agent into the thermoplastic resin particles, the blowing agent may be incorporated into the particles at the same time as the step of obtaining the particles, that is, when impregnating the vinyl aromatic monomer, or during the polymerization of the monomer, or after the polymerization of the monomer is completed. It is added after the flame retardant thermoplastic resin particles are formed.

If a blowing agent is added before polymerization, the blowing agent is added to the suspension of core resin particles with or without dissolving in the vinyl aromatic monomer. When a flame retardant is added during polymerization, it is preferable to dissolve it in the vinyl aromatic monomer and disperse it in an aqueous suspension after the polymerization is completed. Generally, when adding a blowing agent, it is preferable to impregnate the foam under pressure using a pressure-resistant container.

The expandable flame-retardant thermoplastic resin particles obtained by this invention can easily obtain primary expanded particles with a desired expansion ratio, and when molded in a mold using these primary expanded particles, In addition, the primary foamed particles have good fusion properties and can be shaped into any shape, and the foam molded product obtained by foam molding has excellent flame retardancy, as well as weather resistance, chemical resistance, and oil resistance. It is something that has been given a gender.

The flame-retardant thermoplastic resin particles of this invention have excellent chemical resistance and solvent resistance, and are made of vinyl chloride polymer,
Contains vinyl chloride copolymer, which improves chemical resistance and solvent resistance, and since there is no need to use flame retardants, deterioration in weather resistance due to flame retardants is minimized. , it is possible to easily obtain primary foamed particles with a desired expansion ratio, and when molding these primary foamed particles in a mold, each primary foamed particle has good fusion properties and can be formed into any shape. foam can be obtained. Furthermore, since there is no need to use a plasticizer during this foaming, there are various remarkable effects such as no hygienic problems caused by plasticizers.

Next, the present invention will be explained with reference to Examples.

Example 1 100 parts by weight of vinyl chloride polymer (average degree of polymerization 1000) and 3 parts by weight of lead stearate were added, heated and kneaded in an extruder, and extruded to form particulate nuclei with an average diameter of 2 mm and an average length of 4 mm. A material resin was obtained.

1200g of the core material resin particles obtained above were added to the inner volume of 5
The polymer was suspended in an aqueous medium containing 2000 g of water, 4.8 g of metathetical magnesium pyrophosphate, and 10 g of a 2% aqueous solution of sodium dodecylbenzenesulfonate. In this suspension, 2.8 g of benzoyl peroxide and 0.2 g of tert-butyl perbenzoate were added.
A mixed solution of 800 g of styrene monomer was added, and the temperature was raised to 90° C. while stirring at 150 rpm. Polymerization was continued at a temperature of 90°C for 7 hours, and then the temperature was raised to 120°C for 2 hours, followed by cooling to obtain vinyl chloride polymer particles containing heavy styrene inside.

The obtained vinyl chloride polymer is fed to an extruder,
When extruded into a 1 mm thick sheet through a die attached to the tip of an extruder, no layer separation occurred. Even when this sheet was brought close to a candle, it did not burn at all, indicating that the particles obtained above were flame-retardant vinyl chloride polymer particles.

1,000 g of the above vinyl chloride polymer particles are suspended in an aqueous medium obtained by adding 60 g of sodium dodecylbenzenesulfonate to 3,000 g of water in the polymerization vessel, and 200 g of n-butane is forced into the polymerization vessel while stirring the system. Impregnation was carried out at a temperature of 70°C for 6 hours, and the mixture was cooled to a temperature of 20°C, and then taken out from the polymerization vessel and dehydrated and dried.

When the obtained particles were heated at a temperature of 90° C. for 20 seconds, they were foamable flame-retardant vinyl chloride polymer particles that expanded 38 times.

The primary foam particles obtained above are 300mm long and 300mm wide.
It was filled into a mold that could be closed but not sealed, and had a mold cavity of 100 mm and height, and foam molding was performed using steam. When the resulting foamed molded product was broken, each particle was broken, indicating that each particle exhibited extremely excellent fusion properties. When a candle was brought close to this foam molded article and the combustion state was observed, it was found that there was no combustion at all.

Example 2 In Example 1, 1400 g of core resin particles, 600 g of styrene monomer, benzoyl peroxide
Polymerization and blowing agent impregnation were carried out under the same conditions except that 2.1 g of tert-butyl perbenzoate and 0.15 g of tert-butyl perbenzoate were used, and the same tests were also conducted.

The resulting particles are flame retardant and expand 30 times when heated at a temperature of 90° C. for 20 seconds. In addition, the particles were foamable flame-retardant vinyl chloride polymer particles with excellent fusion properties.

Example 3 In Example 1, 1600 g of core resin particles, 400 g of styrene monomer, benzoyl peroxide
Polymerization and blowing agent impregnation were carried out under the same conditions except that 1.4 g and 0.1 g of tert-butyl perbenzoate were used, and the same tests were conducted.

The obtained particles were imparted with flame retardancy, and expanded nine times when heated at a temperature of 90°C for 20 seconds.As a result of foam molding using these particles, each particle was It was a fused foam molded product.

Examples 4 to 5 Same as Example 1 except that the vinyl chloride polymer was replaced with an ethylene-vinyl chloride copolymer containing 5% by weight of ethylene, and the vinyl chloride polymer and chlorinated ethylene polymer were used, respectively. Polymerization and foaming agent impregnation were performed under the following conditions, and the same tests and foam molding were performed.

As a result, primary foamed particles expanded 41 times and 45 times, respectively, were obtained by heating for 20 seconds.

As a result of performing foam molding using these primary foamed particles, a foamed molded product with no shrinkage in which each particle was well fused was obtained.

This foam molded article did not burn at all.

Example 6 In Example 1, 1500 g of core resin particles, 500 g of styrene monomer, benzoyl peroxide
Polymerization and blowing agent impregnation were carried out under the same conditions except that 1.8 g of tert-butyl perbenzoate and 0.15 g of tert-butyl perbenzoate were used.

When the obtained particles were heated at a temperature of 90° C. for 20 seconds, primary expanded particles expanded 15 times in size were obtained.
As a result of performing foam molding using these primary foam particles, a foam molded product was obtained in which each particle was well fused.

Claims (1)

[Claims] 1. Core material resin particles made of vinyl chloride polymer 50~
80% by weight, and 50 to 20% by weight (excluding 50% by weight) of a vinyl aromatic polymer polymerized with the vinyl aromatic monomer substantially absorbed into the particles, Flame-retardant thermoplastic resin particles containing a blowing agent that is gaseous or liquid at room temperature. 2 Core material resin particles made of vinyl chloride polymer 50~
80 parts by weight of vinyl aromatic monomer is suspended in an aqueous medium, and 50 to 20 parts by weight (excluding 50 parts by weight) of vinyl aromatic monomer are added to the suspension and substantially absorbed into the particles to form a polymerization catalyst. A flame-retardant thermal flame retardant, characterized in that it is polymerized in the presence of a gaseous or liquid foaming agent at room temperature and is added before, during, or after the completion of polymerization to obtain resin particles containing a foaming agent. Method for producing plastic resin particles.