JPH06100606A - Method of suspension-polymerizing vinyl monomer - Google Patents

Abstract

PURPOSE:To obtain a vinyl resin excellent in thermal stability, mechanical strength, weatherability, etc., by suspension-polymerizing a vinyl monomer and adding a specific block copolymer to the polymerization system when the conversion is in a given range. CONSTITUTION:100 pts.wt. vinyl monomer (e.g. vinyl chloride) is suspension- polymerized, during which 5-100 pts.wt. block copolymer represented by the formula A-B [wherein A is a block consisting of structural units derived from one or more monomers selected from among (meth)acrylic esters and vinyl esters and B is a block consisting of structural units derived from one or more radical-polymerizable monomers different from the above monomers] is added to the polymerization system when the conversion is 60% or lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension polymerization method for vinyl-based monomers, and more specifically, for suspension polymerization of vinyl-based monomers such as vinyl chloride, a specific block at an early or middle stage of the reaction. The present invention relates to a suspension polymerization method suitable for efficiently producing a vinyl resin having excellent thermal stability, particularly a vinyl chloride resin, by adding a copolymer.

[0002]

2. Description of the Related Art Generally, vinyl resins such as vinyl chloride resin have excellent physical properties such as mechanical strength, weather resistance, chemical resistance and self-extinguishing property, and are suitable for pipes, plates, films, sheets or containers. Although it is widely used, it has a drawback that it has a low softening temperature and therefore is inferior in heat distortion resistance. For example, a hard vinyl chloride resin generally causes a thermal deformation at 70 to 80 ° C., and thus has a problem that it cannot be used at a temperature higher than that.

Conventionally, various methods have been proposed to improve the heat distortion resistance, for example, vinyl chloride-N.
-Allylmaleimide copolymers and the like have been proposed. Although this copolymer has improved heat resistance and excellent fluidity, it has the drawback of being poor in thermal stability and easily dehydrochlorinating during heat molding. In addition, vinyl chloride resin after suspension polymerization,
As a method of blending a so-called heat stabilizer, for example,
Although it has been proposed to add an organotin stabilizer, a lead stabilizer or a violite compound, the thermal stability is still insufficient and it is not practical.

Further, in Japanese Patent Laid-Open No. 2-276847, a vinyl chloride resin, a methyl methacrylate component, N
Selected from the group consisting of alkyl acrylates, methacrylic acid alkyl esters, aromatic vinyl compounds and vinyl cyanide compounds in the presence of a copolymer comprising a substituted maleimide component and an aromatic vinyl component or an elastomer containing a conjugated diene component. A method of blending a copolymer obtained by graft-polymerizing one or more kinds of monomers has been proposed. According to this method, the resin obtained is improved in impact resistance but is still insufficient in thermal stability and is not suitable for practical use.

On the other hand, in suspension polymerization of vinyl chloride monomer, polymethacrylic acid ester such as polymethylmethacrylate (PMMA) or polyacrylic acid ester, polyvinyl ester such as polyvinyl acetate (PVAc), polystyrene, or the like. Suspension polymerization methods in which a polymer such as polyaromatic vinyl is added at a ratio of 1% by weight or less with respect to a vinyl chloride monomer have been conventionally known.
Although it is effective in improving the processing characteristics of the obtained vinyl chloride resin, it has no effect of improving the thermal stability. In addition, there is a fatal drawback that when these polymers are added in an amount of 5% by weight or more based on the vinyl chloride monomer during suspension polymerization, the polymerization stability is adversely affected. Further, as a dispersion aid or a dispersion stabilizer for suspension polymerization having an effect of improving thermal stability, for example, JP-A-3-290402, 3-290403, 3-290404 and 4-93301. Although there are some disclosed in the official gazette, none of them are sufficiently satisfactory.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to retain various physical properties such as mechanical strength, weather resistance, chemical resistance, workability and self-extinguishing property while maintaining heat resistance. It is to develop a suspension polymerization method suitable for producing vinyl resins such as vinyl chloride resins having excellent stability.

[0007]

Means for Solving the Problems The present inventors have made extensive studies in order to achieve the above object. As a result, when suspension polymerization of vinyl-based monomers such as vinyl chloride is carried out, the suspension is obtained by adding a specific AB block copolymer to the reaction system when the conversion rate is relatively low. It has been found that while maintaining the polymerization stability, the thermal stability can be significantly improved without impairing the processing characteristics and various physical properties of the obtained resin. The present invention has been completed based on such findings.

That is, according to the present invention, in carrying out suspension polymerization of a vinyl-based monomer, when the conversion rate is 60% or less, when the conversion rate is 60% or less, 100 parts by weight of the vinyl-based monomer is represented by the following formulas AB: I) (In the formula, A is a block component composed of a structural unit derived from at least one selected from acrylic acid esters, methacrylic acid esters, and vinyl esters,
B is a block component composed of a structural unit derived from at least one kind of radically polymerizable monomer different from A. The present invention provides a suspension polymerization method for a vinyl-based monomer, which comprises adding 5 to 100 parts by weight of the block copolymer represented by (4) to the polymerization system.

The block copolymer used in the present invention is represented by the above formula (I), and is usually one in which the A component and the B component are linearly bonded and both form a main chain. Which means that both the A component and the B component,
Alternatively, it also includes a graft copolymer in which either one is grafted to the main chain. Further, this block copolymer is not limited to one in which the A component and the B component are directly bonded as represented by the above formula (I),
Forms bound via a sulfur atom, such as the formula AS-
Also included are those represented by B (S represents sulfur).

Here, the component A is a block component composed of structural units derived from at least one selected from acrylic acid esters, methacrylic acid esters and vinyl esters. As the acrylic acid ester and methacrylic acid ester (hereinafter, acrylic acid and methacrylic acid may be collectively referred to as (meth) acrylic acid), an alkyl group having 1 to 22 carbon atoms or a cycloalkyl group is usually used. Further, esters having an arylalkyl group are preferable, and specifically, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, ( Amyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
Examples thereof include decyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, and benzyl (meth) acrylate. Examples of vinyl esters include vinyl formate, vinyl acetate, vinyl propionate,
Vinyl butyrate, vinyl isobutyrate, vinyl versatate,
Examples thereof include vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate and vinyl pivalate. When the vinyl ester is saponified and used, the saponification degree is preferably adjusted to 50 mol% or less.

On the other hand, the component B is a block component composed of structural units derived from at least one radically polymerizable monomer different from the component A. Examples of such a monomer include the above-mentioned (meth) acrylic acid esters and vinyl esters provided that they are different from the above-mentioned component A. Further, various monomers such as aromatic vinyl and maleimide compounds can be used. Can be mentioned. Examples of the aromatic vinyl include styrene, α-methylstyrene, o-chlorostyrene, p-chlorostyrene and vinyltoluene. Further, as the maleimide compound, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-tert.
-Butyl maleimide, N-cyclohexyl maleimide,
Examples thereof include N-phenylmaleimide, N-hydroxyphenylmaleimide and N-lauroylmaleimide. Further, as the monomer other than the above which constitutes the component B, (meth) acrylic acid, (meth) acrylic acid amide,
Vinyl ether (eg, methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, etc.), unsaturated dicarboxylic acid (anhydride) (eg, maleic acid, maleic anhydride, chloromaleic anhydride, dichloromaleic anhydride, citraconic anhydride, phenylmalein) Acid anhydride, aconitic acid anhydride, etc., vinyl cyanide (eg acrylonitrile, methacrylonitrile, α-chloroacrylonitrile etc.), vinylpyrrolidone, α-olefin (eg ethylene, propylene etc.), dienes (eg butadiene, Various substances such as isoprene) and derivatives thereof are applicable.

The degree of polymerization of the components A and B of the block copolymer represented by the above formula (I) used in the present invention is not particularly limited, but both components have an average degree of polymerization (Pn).
Is preferably 5000 or less. Further, the block copolymer is not particularly limited in its production method as long as it has the above-mentioned properties, and those produced by various methods can be applied. However, when one of the monomers constituting the A component or the B component (for example, the monomer of the A component) is radically polymerized, thiolcarboxylic acid, 2-acetylthioethylthiol, or 10-acetylthiodecanethiol is used. Polymerized in the presence of a compound containing a thioester and a thiol group in the molecule such as, and the resulting polymer is treated with an alkali such as sodium hydroxide or ammonia to give a polymer having a thiol group at one end. In the presence of this polymer, a method of radically polymerizing a monomer that constitutes the other component (for example, a monomer of component B) is
Most preferred as a method for obtaining a block copolymer simply and efficiently. In this case, the block copolymer (the one represented by the formula A-S-B) in which the A component and the B component are bonded via a sulfur atom is obtained. This manufacturing method is disclosed in
This is described in detail in Japanese Patent Publication No. 9-189111.

The suspension polymerization method of the present invention proceeds by adding the above block copolymer to a reaction system for carrying out suspension polymerization of vinyl monomers. The time when the conversion rate of the vinyl-based monomer is 60% or less, preferably 30% or less, more preferably 10% or less, particularly preferably at the time of initiation of polymerization or before initiation. If added after the conversion of the vinyl monomer exceeds 60%, the block copolymer and the vinyl monomer are not sufficiently mixed, and the desired effect is not exhibited. The amount of the block copolymer added is 5 to 100 with respect to 100 parts by weight of the vinyl-based monomer which is a polymerization raw material.
Parts by weight, preferably 20 to 80 parts by weight, more preferably 40 to 70 parts by weight.

In the suspension polymerization method of the present invention, a dispersion stabilizer can be used if necessary. As the dispersion stabilizer, a vinyl monomer such as vinyl chloride is suspended in an aqueous medium. It may be one usually used in the polymerization, such as water-soluble cellulose ethers such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and hydroxypropyl methyl cellulose, partially saponified polyvinyl alcohol (saponification degree 60 to 95 mol%, average degree of polymerization). 500 or more) and modified products of this ionic group or nonionic group, low saponification degree polyvinyl alcohol (saponification degree of less than 60 mol%, average polymerization degree of 3000 or less) and modified products of this ionic group or nonionic group, water-soluble polymers such as gelatin, sorbitan Monolaurate, sorbitan trioleate, green Examples thereof include oil-soluble emulsifiers such as phosphorus tristearate and ethylene oxide propylene oxide block copolymers, water-soluble emulsifiers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, and sodium laurate. These may be used alone or in combination of two or more. Added in combination. The amount added is not particularly limited, but is preferably 0.03 to 0.15 part by weight per 100 parts by weight of vinyl-based monomer such as vinyl chloride.

Various other additives can be added as required. Various additives that can be used include acetaldehyde, butyraldehyde, trichlorethylene, perchlorethylene, mercaptans, and other polymerization degree regulators, and phenol compounds, sulfur compounds, N-oxide compounds, and other polymerization inhibitors. Also, a pH adjuster,
It is optional to add scale inhibitors, cross-linking agents, etc.
A plurality of the above additives may be used in combination without any problem. It is also effective to attach a condenser such as a condenser to the polymerization apparatus.

On the other hand, the polymerization initiator may also be one which has been conventionally used for the polymerization of vinyl monomers such as vinyl chloride, which includes diisopropyl peroxydicarbonate and di-
Percarbonate compounds such as 2-ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate, t-butyl peroxyneodecanate, α
-Perester compounds such as cumyl peroxyneodecanate and t-butyl peroxyneodecanate, acetylcyclohexylsulfonyl peroxide and 2,4,4
-Peroxides such as trimethylpentyl-2-peroxyphenoxyacetate, 2,2'-azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile,
Examples thereof include azo compounds such as azobis (4-methoxy-2,4-dimethylvaleronitrile), and these can also be used in combination with potassium persulfate, ammonium persulfate, hydrogen peroxide and the like. This added amount is
0.0 per 100 parts by weight of vinyl-based monomers such as vinyl chloride
A range of 2 to 0.3 parts by weight is preferred.

Further, the AB block copolymer represented by the above formula (I) is added to 5 parts by weight of 100 parts by weight of the vinyl monomer at a conversion rate of the vinyl monomer of 60% or less. -10
If 0 parts by weight is added, the charging ratio of each component, the charging sequence, the polymerization temperature, etc. should be determined according to the conditions conventionally used for suspension polymerization of vinyl monomers such as vinyl chloride. Well, there is nothing to limit. There is no particular limitation on the charging temperature of water used for the polymerization, and it may be 40 ° C.
A so-called hot charge method in which warm water of ~ 95 ° C is charged can also be used.

There are various vinyl monomers as raw material monomers used in the suspension polymerization method of the present invention. Specifically, in addition to vinyl chloride alone, a monomer containing vinyl chloride as a main component As a comonomer copolymerized with vinyl chloride, a vinyl ester such as vinyl acetate, vinyl propionate, methyl (meth) acrylate, ethyl (meth) acrylate is included. Examples thereof include (meth) acrylic acid esters such as ethylene, olefins such as ethylene and propylene, maleic anhydride, acrylonitrile, itaconic acid, styrene, vinylidene chloride, vinyl ether, and other monomers copolymerizable with vinyl chloride. Furthermore, the suspension polymerization method of the present invention can also be employed in homopolymerization or copolymerization of the above vinyl-based monomer containing no vinyl chloride.

If necessary, various rubber components may be added to the vinyl resin such as the vinyl chloride resin obtained by the suspension polymerization method of the present invention. Examples of the rubber component that can be added here include polybutadiene, styrene-butadiene block polymer, nitrile rubber, maleated rubber, polyisoprene rubber, butadiene-acrylonitrile rubber, ethylene-propylene-diene terpolymer, butadiene-styrene-butadiene. Examples thereof include terpolymers and butadiene-isoprene-butadiene terpolymers. Similarly, metal soaps such as calcium stearate, zinc stearate, barium stearate, cadmium stearate and lead stearate, which have been conventionally used as stabilizers for vinyl chloride resins, dibasic sulfates, dibasic stearin. Lead acid,
Inorganic stabilizers such as calcium hydroxide and calcium silicate,
Furthermore, lubricants, pigments, fillers, impact modifiers, processing aids, UV absorbers, etc. may be added later.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the following examples, "%" and "parts" mean "% by weight" and "parts by weight" unless otherwise specified. The block copolymers used in the following examples are the A-S-B type in which the A component and the B component are linked by a sulfide bond synthesized by the method described in JP-A-59-189111. It is a block copolymer.

Example 1 Dispersant (dispersion stabilizer) composed of polyvinyl alcohol (PVA) having a saponification degree of 70 mol% and an average polymerization degree of 700.
And suspension polymerization of vinyl chloride was carried out by the following method using the block copolymers shown in Table 1. That is, a glass-lined autoclave was charged with 50 parts of deionized water, 0.06 part of the dispersant, 5 parts of the block copolymer and 0.009 part of a 50 wt% toluene solution of diisopropyl peroxydicarbonate, and the inside of the autoclave was set to 50 m.
After degassing to reach mHg to remove oxygen, 30 parts of vinyl chloride was charged, and the temperature was raised to 57 ° C. with stirring to carry out polymerization. At the start of polymerization, the pressure inside the autoclave is 8.0 kg /
cm ² G, but 6 hours after initiation of polymerization 5.0 kg / c
Since m ² G was reached, the polymerization was stopped at this point, unreacted vinyl chloride monomer was purged, the contents were taken out and dehydrated and dried. Dispersant (dispersion stabilizer) used for suspension polymerization and A
The type and amount of the -B block copolymer are shown in Table 1, and the performance of the obtained vinyl chloride resin is shown in Table 2.

Examples 2 to 10 and Comparative Examples 1 to 7 Examples except that the type and amount of the dispersant (dispersion stabilizer) and AB type block copolymer were changed as shown in Table 1. Suspension polymerization of vinyl chloride was carried out in the same manner as in 1.
The performance of the obtained vinyl chloride resin is shown in Table 2.

[0023]

[Table 1]

[0024]

[Table 2]

MMA: methyl methacrylate BA: n-butyl acrylate MA: methacrylic acid 2EHA: 2-ethylhexyl acrylate VAc: vinyl acetate PVi: vinyl pivalate NPM: N-phenylmaleimide EVA: ethylene-vinyl acetate MAA: anhydrous Maleic acid NCHM: N-cyclohexylmaleimide St: Styrene

[0026]

[Table 3]

In Table 2, the average particle size and thermal stability of the obtained vinyl chloride resin were measured by the following methods. [Average particle diameter] The average particle diameter was measured by dry sieving analysis using a Tyler mesh standard wire mesh. [Thermal Stability] The vinyl chloride resin obtained by suspension polymerization was dried at 65 ° C. for 8 hours, and then the particles were heated in a hot block bath at 170 ° C. to visually determine the degree of coloring. ◎ Not colored ○ Slightly colored △ Colored pink × Colored red to brown

[0028]

As is apparent from the above description, the vinyl resin such as the vinyl chloride resin produced by the suspension polymerization method of the present invention has a large particle size, so that scattering during handling thereof is small, and Since it has excellent thermal stability, it is less likely to be colored during processing, and its handling is easy. Therefore, the suspension polymerization method of the present invention is extremely useful in practical use as a method for producing a vinyl resin having excellent physical properties and processing characteristics.

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[Procedure amendment]

[Submission date] November 6, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the following examples, "%" and "parts" mean "% by weight" and "parts by weight" unless otherwise specified. The block copolymers used in the following examples are the A-S-B type in which the A component and the B component are linked by a sulfide bond synthesized by the method described in JP-A-59-189111. It is a block copolymer. The amounts of dispersant and block copolymer used in the following Examples and Comparative Examples are based on 100 parts of vinyl chloride.

Claims (1)

[Claims] 1. When carrying out suspension polymerization of a vinyl-based monomer, the vinyl-based monomer 10 is added at a conversion rate of 60% or less.
With respect to 0 parts by weight, a compound of the formula AB (wherein A is a block component composed of a structural unit derived from at least one selected from acrylic acid esters, methacrylic acid esters and vinyl esters,
B is a block component composed of a structural unit derived from at least one kind of radically polymerizable monomer different from A. 5) 100 parts by weight of the block copolymer represented by 4) is added into the polymerization system.