JPH04202443A - Production of expandable vinyl resin particle - Google Patents

Abstract

PURPOSE:To obtain, in a short time, stable expandable vinyl resin particles giving a foam having a uniform cell structure by copolymerizing a vinyl monomer and an organosilicon compd. having a double bond copolymerizable with the vinyl monomer in suspension in an aq. medium and impregnating a blowing agent into the resulting copolymer particles. CONSTITUTION:A vinyl monomer (e.g. styrene) and an organosilicon compd. having a double bond copolymerizable with the vinyl monomer (e.g. methacryloly loxyalkyltristrialkylsiloxysilane) are copolymerized in suspension in an aq. medium. During or after the polymn., a blowing agent (e.g. propane) is impregnated into the resulting copolymer particles, giving expandable vinyl resin particles. The organosilicon compd., which contributes to stabilize the dispersion of suspended particles during polymn., is used pref. in an amt. of 0.1-15 pts.wt. based on 100 pts.wt. the vinyl monomer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an improved method for producing expandable vinyl resin particles.

(Prior art) Vinyl resin particles contain aliphatic hydrocarbons such as propane, butane, and pentane, cycloaliphatic hydrocarbons such as cyclobutane and cyclopentane, methyl chloride, monochloroethane, dichloroethane, and dichlorofluoroethane. Those impregnated with easily volatile foaming agents such as halogenated hydrocarbons in an amount of 1 to 20% by weight based on the weight of the vinyl resin particles are known as expandable vinyl resin particles.

When such expandable vinyl resin particles are heated to a temperature higher than their softening point with water vapor or the like, the expandable vinyl resin particles contain a large number of closed cells (hereinafter referred to as cells) with a size of several tens to hundreds of μm. , and pre-expanded particles having a volume several times to several hundred times that of the expandable vinyl resin particles can be obtained. Next, these pre-expanded particles are filled into a closed mold that can be heated inside with steam or the like through small holes or slits, and when heated with steam, etc., the pre-expanded particles become foamed particles whose volume has further expanded by about 1.5 times. The voids between the foamed particles are eliminated, the pre-expanded particles are brought into close contact with each other, and the vicinity of the surface of the pre-expanded particles is melted by heat such as water vapor, and the pre-expanded particles are melted and pressed together, thereby forming the closed mold. It is known that foamed vinyl molded products (hereinafter referred to as foamed molded products) can be easily manufactured, and the foamed molded products made in this way can be used as various cushioning materials, insulation materials, and packaging materials. Used for containers, etc.

It is well known that the quality characteristics such as the strength of these foamed molded products are greatly influenced by the size and uniformity of the cell diameter of the pre-expanded particles. In order to obtain this, ethylene bisstearylamide additives (hereinafter referred to as EBS, etc.) and hexabromocyclododecane additives (hereinafter referred to as HBCD, etc.) are added during the suspension polymerization reaction of vinyl monomers. It is known.

(Problem to be solved by the invention) However, EBS etc. make the dispersion of suspended particles unstable during suspension polymerization reaction, and HBCD etc. act as a chain transfer agent in suspension polymerization, so polymerization time is unnecessary. This poses the major problem of causing long delays.

(Means for Solving the Problems) As a result of extensive research to solve the above problems, the present inventors copolymerized an organosilicon compound capable of copolymerizing with a vinyl group together with a vinyl monomer. and EBS etc.
It was discovered that the cell diameter could be adjusted and pre-expanded particles having a uniform cell diameter could be obtained without adding BCD or the like, and the present invention was completed.

That is, the present invention provides an aqueous solution containing as essential components a vinyl monomer (A) and an organosilicon compound (B) having one double bond copolymerizable with the vinyl monomer (A). An object of the present invention is to provide a method for producing expandable vinyl resin particles, which comprises carrying out suspension polymerization in a medium and impregnating a blowing agent into the copolymer particles during or after the polymerization.

Examples of the vinyl monomer (A) used in the present invention include styrene; NW-converted styrenes such as α-methylstyrene, vinyltoluene, chlorostyrene, and divinylbenzene;
Hinyl cyanide compounds such as acrylonitrile; acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, and hydroxyethyl acrylate; methacrylic esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and hydroxyethyl methacrylate; maleic anhydride, etc. One or more types of unsaturated carboxylic acid anhydrides can be used.

Furthermore, in the present invention, the styrenic monomer is one that contains 50% by weight or more of styrene or the various substituted styrenes mentioned above in the vinyl monomer (A). Incidentally, it is not necessary to select a styrene monomer as the vinyl monomer (A), but in consideration of raw material cost, foaming agent retention, foaming ratio, etc., a styrene monomer, especially a styrene monomer, may be selected. It is desirable to use a material containing 50% by weight or more of styrene, especially styrene.

As the organosilicon compound (B) used in the present invention,
Any organosilicon compound having one double bond copolymerizable with the vinyl monomer (A) can be used, but it usually has an average molecular weight of 300 to 10,000, preferably an average molecular weight of 400 to 2,000. For example, (meth)acryloxyalkyltristriphenylsiloxysilane, (meth)acryloxyalkyltristriphenylsiloxysilane, silicone acrylate oligomer, vinyl-modified silicone oligomer, etc. are used.

Structural formulas of some of these organosilicon compounds (B) are shown below, and among them, γ-(meta) shown by structural formula (1)
Preferably, those having a tristrialkylsiloxy group at the end, such as acrylo-cow dialkyl tristrialkyl silo-cow disilane and silicone acrylate represented by structural formula (2), are preferred.

・ ・ (2) ・ -(3) A method of reacting trialkylsiloxysilane or phenylsiloxysilane (1) with a cone acrylate oligomer (7) with a warped cone such as an acid group. Examples of the oligomer include a method of copolymerizing a vinylmonoalkyldialkoxysilane and a vinylmonoalkyldialkoxysilane.

The amount of the organosilicon compound (B) used in the present invention is
Although it is determined as appropriate depending on the type of vinyl monomer (A) and is not necessarily limited, usually vinyl monomer (A) 10
It is used in an amount of 0.1 to 15 parts by weight relative to 0 parts by weight. Among these, when a styrene monomer is used as the vinyl monomer, it is most preferably used in an amount of 0.1 to 10% by weight based on 100 parts by weight of the styrene monomer.

Further, the organosilicon compound (B) used in the present invention may be added to the reaction system at any time before or during the polymerization reaction. Further, the vinyl resin particles are suspended in an aqueous medium, and the vinyl monomer (A) and the organosilicon compound (B) are added to the suspension, respectively.
Alternatively, they may be added as a mixture and copolymerized. Among them, when using those having a trialkylsiloxy group or tristriphenylsiloxy group at the end, it is preferable to add them before the polymerization reaction or at the beginning of the polymerization reaction.When using other substances,
It is preferable to add it during the polymerization reaction.

In the present invention, it is preferable to use a polymerization initiator during polymerization of the vinyl resin particles, and examples of the polymerization initiator include benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-phytyl peroxide, 2,
5-di(beloki/henshade)hexyne-3,1,
3-bis(1-butylperoxyisopropyl)benzene, lauroyl peroxide, t-butyl peracetate, 2
゜5-dimethyl-2,5-di(t-butylperoxy)
Organic peroxides such as hexyne-3,2,5-dimethyl-2,5-di(t-butylperoxy) hexasan, and t-butyl perbenzoate, methyl ethyl ketone peroxide, and methylcyclohexanone peroxide; azobis Ab-based compounds such as -isobutyronitrile and dimethyl azodiisobutyrate are mentioned, and these can be used alone or in a mixture of two or more. The amount used is determined as appropriate depending on the types of the vinyl monomer (A) and the organosilicon compound (B) and the desired molecular weight of the resulting resin particles. ) and organosilicon compound (B) in total of 100 parts by weight.
It is preferable to use 1 to 4% by weight.

The foaming agent used in the present invention has a boiling point lower than the softening point of the vinyl resin particles to be foamed, and has the property of not dissolving the vinyl resin particles or causing them to swell slightly. Such blowing agents include, for example, aliphatic hydrocarbons such as propane, butane, or pentane; cycloaliphatic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane; methyl chloride, monochloroethane, dichloroethane, or dichloroethane; Easily volatile blowing agents such as halogenated hydrocarbons such as chlorofluoroethane and the like can be mentioned. The amount of this blowing agent used is usually 1 to 20 parts by weight per 100 parts by weight of the expandable vinyl resin particles, unreacted vinyl monomer (A), and unreacted organic Noricone compound (B). be.

When propane, butane, pentane, cyclohexan, etc. are used alone or in combination among the above blowing agents, it is preferable to use an organic solvent that dissolves the vinyl resin particles during impregnation with the blowing agent.

Examples of such organic solvents include aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; halogenated hydrocarbons such as ethylene dichloride, trichlorethylene, and tetrachloroethylene; and known and commonly used organic solvents such as esters such as ethyl acetate and butyl acetate. Mention may be made of solvents. The amount of this organic solvent used is usually 0.00 parts by weight per 100 parts by weight of the expandable vinyl resin particles, unreacted vinyl monomer (A), and unreacted organic silicon compound (B).
It is 1 to 5 parts by weight.

For impregnation with a blowing agent, the blowing agent is added to the aqueous medium during polymerization, but it can also be carried out by adding the blowing agent into the system after the polymerization is complete with the resin particles suspended in the aqueous medium. . In addition, when adding a blowing agent during the polymerization, the vinyl monomer (A) and the organosilicon compound (B)
From the viewpoint of stability of the polymerization system, it is preferable to carry out the reaction after the conversion rate of the monomer consisting of is 50% by weight or more.

In the present invention, the vinyl monomer (A) and the organosilicon compound (B) are polymerized in an aqueous medium,
In this case, a poorly soluble phosphate, a water-soluble polymer protective colloid, etc. can be added to the polymerization system as a dispersant. Examples of poorly soluble phosphates include tricalcium phosphate and magfusium phosphate. In addition, examples of the polymeric protective colloid include water-soluble cellulose conductors such as polyvinyl alcohol, alkylcellulose, hydrodialkylcellulose, and carboxyalkylcellulose;
Examples include sodium polyacrylate. The content of the sparingly soluble phosphate is 0.01% by weight or more based on the total amount of the polymerization system, and the content of the water-soluble polymer protective colloid is 0.001 to 1% by weight based on the total amount of the polymerization system. Preferably used.

In the present invention, in addition to the above, anionic surfactants such as sodium dodecylhensensulfonate; water-soluble inorganic salts such as sodium hydroxide and calcium hydroxide may also be used in combination.

In addition, in the polymerization process of the expandable vinyl resin particles according to the present invention, known additives such as flame retardants, antistatic agents, antioxidants, pigments, etc. may be included.

Furthermore, various known modifiers such as anti-blocking agents during pre-foaming, molding cycle improvers and antistatic agents during molding are added to the surface of the expandable vinyl resin particles obtained by the present invention. may be applied.

(Example) The present invention will be specifically described below with reference to Examples and Comparative Examples.

Example 1 In a 5Q autoclave equipped with a rotary stirrer, 2000 g of ion-exchanged water, 2000 g of styrene, and 2 g of γ-methacryloxypropyltristrimethylsiloxysilane were added.
．． After starting stirring, 5.0 g of basic phosphate and 0.003 g of potassium persulfate were added, and 6.0 g of hensyl peroxide and 2.0 g of t-butylperhenzoet were added. A suspension polymerization reaction was carried out at 90°C for 6 hours to form polystyrene particles.

Next, 30g of toluene was added, and after 15 minutes, 1 butane gas was added.
After 40 g was injected, the temperature was raised to 120°C at a rate of 15°C/hour, and the reaction was continued at this temperature for an additional 2 hours. After the reaction was completed, the contents were cooled to 25°C and extracted, dried and sieved to obtain expandable vinyl resin particles with a particle size of 0.84 to 1.41 mm, and the average particle size and particle size distribution slope n and weight average molecular weight were measured. The results are shown in Table 1.

Next, the resin particles are heated with steam to give a bulk ratio of 60.
The pre-expanded particles were made into pre-expanded particles, and after aging for about 24 hours, the cell diameter of the pre-expanded particles was measured. In addition, these pre-expanded particles were filled into a closed mold, heated with steam to melt and press together to obtain a foamed molded product with a beautiful surface and a good fusion rate, and the fusion rate of the expanded particles of this molded product was measured. did. The results are shown in Table 2.

Example 2 Expandable vinyl resin particles were obtained in the same manner as in Example 1 except that the amount of γ-methacryloxypropyltristrimethylsiloxysilane added was changed to 100 g, and the average particle size, particle size distribution slope n, and weight average were obtained. The molecular weight was measured. The results are shown in Table 1.

Next, using the obtained resin particles, a foamed molded article having a beautiful surface and a good fusion rate with the pre-expanded particles was obtained in the same manner as in Example 1, and the cell diameter of the pre-expanded particles and the fusion of the expanded particles of the molded article were The adhesion rate was measured. The results are shown in Table 2.

Example 3 In a 5Q autoclave equipped with a rotary stirrer, 2000 g of ion-exchanged water, 2000 g of styrene, and 2 g of γ-methacryloxypropyltristrimethyluroxysilane were added.
．． After starting stirring, 5.0 g of basic phosphate and potassium persulfate were added, followed by 6.0 g of pensoyl peroxide and 2.0 g of t-butylbergensoeth. After adding Og, a suspension polymerization reaction was carried out at 90'C for 6 hours to form polystyrene particles, and after cooling,
Drying and sieving were performed to obtain expandable vinyl resin particles having a size of 084 to 1.41 mrIl. Next, in a 5Q autoclave equipped with a rotary stirrer, 3000 g of ion-exchanged water, 5.0 g of basic phosphate, 0.04 g of sodium dodenlebenzenesulfonate, and 100 g of the above polystyrene particles were added.
After heating to 90°C with stirring, 15g of toluene was added, and after 15 minutes, 70g of butane gas was introduced under pressure, and the temperature was raised to 120°C at a rate of 15°C/hour. Allowed time to react. After the reaction was completed, the contents were cooled to 25° C., then the contents were extracted and dried to obtain expandable vinyl resin particles, and the average particle size, particle size distribution slope n, and weight average molecular weight were measured. The results are shown in Table 1.

Next, using the obtained resin particles, a foamed molded article having a beautiful surface and a good fusion rate with the pre-expanded particles was obtained in the same manner as in Example 1, and the cell diameter of the pre-expanded particles and the fusion of the expanded particles of the molded article were The adhesion rate was measured. The results are shown in Table 2.

Example 4 The same procedure as Example 1 was carried out, except that 2 g of γ-methacryloquinepropyltristrimethylsiloxysilane was added to the suspension polymerization system not before polymerization, but after the polymerization conversion rate of styrene reached 30% by weight. Expandable vinyl resin particles were obtained, and the average particle diameter, particle size distribution slope n, and weight average molecular weight were measured. The results are shown in Table 1.

Next, using the obtained resin particles, a foamed molded article having a beautiful surface and a good fusion rate with the pre-expanded particles was obtained in the same manner as in Example 1, and the cell diameter of the pre-expanded particles and the fusion of the expanded particles of the molded article were The adhesion rate was measured. The results are shown in Table 2.

Example 5 In place of γ-methacryloxypropyltristrimethylsiloxysilane, a compound represented by the following structural formula was added to the suspension polymerization system at 7 points when the planned styrene polymerization conversion was 60% by weight, not before polymerization. 2g per
Expandable vinyl resin particles were obtained in the same manner as in Example 1, except that the particles were added, and the average particle diameter, particle size distribution slope n, and weight average molecular weight were measured. The results are shown in Table 1.

Next, using the obtained resin particles, a foamed molded article having a beautiful surface and a good fusion rate with the pre-expanded particles was obtained in the same manner as in Example 1, and the cell diameter of the pre-expanded particles and the fusion of the expanded particles of the molded article were The adhesion rate was measured. The results are shown in Table 2.

Example 6 In a 5Q autoclave equipped with a rotary stirrer, 2000 g of ion-exchanged water, 5.0 g of basic phosphate, 0.04 g of sodium dodecylbenzenesulfonate, and the particles were classified to have a particle size range of 0.71 to 1.14. A certain polystyrene particle 1
Add 800 g of styrene and raise the temperature to 90°C with stirring, then add 202 g of a solution of 2 g of γ-methacryloxypropyltristrimethylsiloxysilane dissolved in 200 g of styrene, 0.58 g of hensyl peroxide, and 0.0 .2g was added over 10 minutes, 30g of toluene was added after 30 minutes, 140g of butane gas was injected after another 15 minutes, the temperature was raised to 120°C at a rate of 15°C/hour, and the reaction was continued at this temperature for another 2 hours. I let it happen. After the reaction was completed, the contents were cooled to 25° C., and the contents were extracted and dried to obtain expandable vinyl resin particles, and the average particle size, particle size distribution slope n, and weight average molecular weight were measured. Table 1 shows the results.
Shown below.

Next, using the obtained resin particles, a foamed molded article having a beautiful surface and a good fusion rate with the pre-expanded particles was obtained in the same manner as in Example 1, and the cell diameter of the pre-expanded particles and the fusion of the expanded particles of the molded article were The adhesion rate was measured. The results are shown in Table 2.

Comparative Example 1 Expandable vinyl resin particles were obtained in the same manner as in Example 1 except that the addition of γ-methacryloxypropyltristrimethylsiloxysilane was omitted, and the average particle size and particle size distribution slope n
and weight average molecular weight were measured. The results are shown in Table 1.

Next, using the obtained resin particles, pre-expanded particles and a foamed molded article were obtained in the same manner as in Example 1, and the cell diameter of the pre-expanded particles and the fusion rate of the expanded particles of the molded article were measured. The cells of the foamed particles were non-uniform, and the fusion rate of the foamed molded product was poor. The results are shown in Table 2.

Comparative Example 2 Expandable vinyl resin particles were obtained in the same manner as in Example 1, except that the addition of γ-methacryloxypropyltristrimethylsiloxysilane was omitted and 2 g of ethylene bistristearylamide was added, and the average particle size and particle size were The distribution slope n and weight average molecular weight were measured, but the dispersion system during polymerization was unstable and the polystyrene particles had a wide particle size distribution.

The results are shown in Table 1.

Next, using the obtained resin particles, pre-expanded particles and a foamed molded article were obtained in the same manner as in Example 1, and the cell diameter of the pre-expanded particles and the fusion rate of the expanded particles of the molded article were measured. Although the cells of the pre-expanded particles were uniform, the fusion rate of the foamed molded product was poor. The results are shown in Table 2.

Comparative Example 3 Expandable vinyl resin particles were obtained in the same manner as in Example 1, except that the addition of γ-methacryloxypropyltristrimethylsiloxysilane was omitted and hexabromocyclododecane was added, and the average particle size and particle size distribution were The slope n and weight average molecular weight were measured, but the dispersion system during polymerization was unstable.
The polystyrene particles had a wide particle size distribution. The results are shown in Table 1.

Next, using the obtained resin particles, pre-expanded particles and a foamed molded article were obtained in the same manner as in Example 1, and the cell diameter of the pre-expanded particles and the fusion rate of the expanded particles of the molded article were measured. Although the cells of the pre-expanded particles were uniform, the fusion rate of the foamed molded product was poor. The results are shown in Table 2.

Table 1 Table 2 *1) Particle size distribution slope n: The slope n of the particle size distribution is determined by measuring the percentage above the sieve, and calculating the percentage above the sieve for each measured particle size using the formula (I) below for the Rosin-Ramler particle size distribution. It was calculated using the method of least squares.

2-12-1oβxn... (I) In the formula, n: slope
The diameter of the closed cells cut at the center was measured and the average value was calculated.

*3) Molded product fusion rate: A plate-shaped molded product was broken and broken at the center, and the fusion rate of particles on the fractured surface was measured.

(Effects of the Invention) According to the production method of the present invention, the dispersion of suspended particles during suspension polymerization is stabilized, and unnecessary delays in polymerization time are eliminated. Also,
Even after manufacturing, EBS etc. and HBCD are commonly used.
It bleeds out from the suspended particles to the surface of the suspended particles like non-reactive additives such as, does not cause product changes over time, and has the uniform cell diameter that was previously required. Pre-expanded particles of expandable vinyl resin can be obtained.

Claims (1)

[Claims] 1. Vinyl monomer (A) and the vinyl monomer (A)
and an organosilicon compound (B) having one copolymerizable double bond as essential components, which are subjected to suspension polymerization in an aqueous medium, and a blowing agent is impregnated into the copolymer particles during or after the polymerization. A method for producing expandable vinyl resin particles. 2. The organosilicon compound (B) is selected from the group consisting of (meth)acryloxyalkyltristrylkylsiloxysilane, (meth)acryloxyalkyltristriphenylsiloxysilane, silicone acrylate oligomer, and vinyl-modified silicone oligomer.
The manufacturing method according to claim 1, wherein the compound is more than one species. 3. The manufacturing method according to claim 2, wherein the organosilicon compound (B) is a compound having a trialkylsiloxy group. 4. The manufacturing method according to claim 1, wherein the organosilicon compound (B) is γ-methacryloxypropyltristrimethylsiloxysilane. 5. Claim 1, 2 or 3, wherein the vinyl monomer (A) is a styrenic monomer containing 50% by weight or more of styrene.
Manufacturing method described. 6. Claim 1, wherein the vinyl monopolymer (A) is styrene.
, 2 or 3.