JPH0753607A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To produce a vinyl chloride polymer having a highly porous particle structure, excellent processability and low fish-eye content by polymerizing vinyl chloride in the presence of a partially saponified polyvinyl alcohol as a dispersing agent while adding a suspending agent to the system. CONSTITUTION:Vinyl chloride or a monomer mixture containing vinyl chloride is suspension polymerized in an aqueous medium in the presence of 0.01-5 pts.wt. (based on 100 pts.wt. of the monomer) of a partially saponified polyvinyl alcohol having an average polymerization degree of 150-600 and a saponification degree of 20-60mol% as a dispersing agent while continuously or intermittently adding a suspension agent having a water solubility higher than that of the alcohol from the start of polymerization until the polymerization ratio reaches 5-50%. The suspension agent is a water-soluble partially saponified polyvinyl alcohol having an average polymerization degree of 700-3,000 and a saponification degree of 70-85mol% or a hydroxypropylmethylcellulose having a me thoxy substitution degree of 26-30wt.% and a hydroxypropoxy substitution degree of 4-15wt.% and the compounding amount of the suspension agent is 0.03-0.1 pts.wt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl chloride polymer by suspension polymerization. More specifically, it has a particle structure with high porosity and is excellent in processability. The present invention relates to a method for producing a vinyl chloride polymer having less fish eyes when used.

[0002]

2. Description of the Related Art Conventionally, many methods for producing vinyl chloride polymers have been proposed for the purpose of improving processability, reducing generation of fish eyes, and improving blendability. For example, JP-A Nos. 52-5866 and 52-15890.
No. 55-112210, No. 53-6392, Japanese Patent Publication No. 61-18562, etc., a so-called oil-soluble polyvinyl alcohol having a saponification degree of 55 mol% or less and an average polymerization degree of 600 or less is used as a dispersant. A method for producing a vinyl chloride-based polymer is disclosed, in which vinyl chloride, which is a monomer, is suspended and dispersed in an aqueous medium to carry out suspension polymerization.

On the other hand, a method for reducing fish eyes when a polymer plasticizer is used is disclosed in Japanese Patent Laid-Open No. 61-40326.

[0004]

However, the vinyl chloride polymer obtained by the method of the above publication has a high porosity to some extent and reduces the generation of fish eyes, but the degree is still sufficiently satisfactory. is not.
Further, recently, in order to obtain a soft polyvinyl chloride resin composition having excellent oil resistance and extraction resistance, a high molecular weight plasticizer such as polyester or EVA is used instead of a low molecular weight plasticizer such as phthalate ester. Often used, vinyl chloride polymer may be subjected to processing under a condition of shallow kneading, and under such conditions, the vinyl chloride polymer obtained by this method has increased fish eyes. Inconvenience occurs.

The present invention has been made in view of the above circumstances and has high porosity, good processability, and little fish eyes even when kneading is shallow by using a polymer plasticizer. An object is to provide a method for producing a vinyl chloride polymer.

[0006]

MEANS TO SOLVE THE PROBLEMS As a result of intensive studies to achieve the above-mentioned object, the present inventor found that vinyl chloride or a monomer mixture containing vinyl chloride was suspended and dispersed in an aqueous medium. In the method for producing a vinyl chloride polymer for carrying out suspension polymerization, at the start of suspension polymerization, a partially saponified polyvinyl alcohol having an average degree of polymerization of 150 to 600 and a degree of saponification of 20 to 60 mol% is charged as a dispersant. Quantum 10
Polymerization is initiated by using 0.01 to 5 parts by weight per 0 part by weight, and a suspending agent having higher water solubility than the partially saponified polyvinyl alcohol is continuously or sequentially added from the initiation of polymerization to obtain a polymerization rate. The addition should be terminated when 5 to 50% is reached, in which case the average degree of polymerization is 700 to 3 as a suspending agent added continuously or sequentially from the start of polymerization.
000, a water-soluble partially saponified polyvinyl alcohol having a saponification degree of 70 to 85 mol% and / or a methoxy substitution degree of 2
6-30% by weight, hydroxypropoxy substitution degree 4-1
By using 0.03 to 0.1 part by weight of 5% by weight and a 2% by weight aqueous solution of hydroxypropylmethylcellulose having a viscosity at 20 ° C. of 5 to 4000 cps, high porosity and good processability can be obtained. It has been found that a vinyl chloride polymer in which generation of fish eyes is effectively suppressed can be obtained even when molding is performed under a wide range of processing conditions.

That is, when the above-mentioned oil-soluble partially saponified polyvinyl alcohol is used as a dispersant at the start of the polymerization, the suspension system can be stabilized and the generation of scale can be prevented. The suspension system could not be kept stable over the entire period, and by adding a water-soluble suspending agent continuously or sequentially simultaneously with the start of polymerization, the suspension stability was maintained over the entire period of polymerization. It was found that a good polymer having a high porosity and a small fish eye can be obtained by maintaining the above-mentioned value and preventing the scale from adhering, and thus the present invention has been accomplished.

Accordingly, the present invention provides a method for producing a vinyl chloride-based polymer, wherein vinyl chloride or a monomer mixture containing vinyl chloride is suspended and dispersed in an aqueous medium to carry out suspension polymerization. Degree of 150-600, saponification degree of 2
The polymerization is initiated by using 0 to 60 mol% of partially saponified polyvinyl alcohol as a dispersant in an amount of 0.01 to 5 parts by weight per 100 parts by weight of the charged monomer, and (2) more water-soluble than the partially saponified polyvinyl alcohol. A suspension agent having a high
The method for producing a vinyl chloride-based polymer, characterized in that the addition is terminated when it reaches 50%, and the suspension agent added from the start of the polymerization has an average degree of polymerization of 700 to 3000,
Water-soluble partially saponified polyvinyl alcohol having a saponification degree of 70 to 85 mol% and / or a methoxy substitution degree of 26 to 30
% By weight, hydroxypropoxy substitution degree is 4-15% by weight
And the viscosity of the 2% by weight aqueous solution at 20 ° C. is 5
Provided is a method for producing the above vinyl chloride-based polymer, which comprises using 0.03 to 0.1 part by weight of hydroxypropylmethylcellulose having a concentration of ˜4000 cps.

The present invention will be described in more detail below. In the method for producing a vinyl chloride polymer of the present invention, the vinyl chloride or a monomer mixture containing vinyl chloride is suspended and dispersed in an aqueous medium as described above. When suspension polymerization is carried out by using a specific dispersant at the start of polymerization.

Here, in the present invention, as such a dispersant,
Average degree of polymerization is 150-600, preferably 150-40
0, the degree of saponification is 20 to 60 mol%, preferably 40 to 6
0 mol% of oil-soluble partially saponified polyvinyl alcohol is used. If the average degree of polymerization is less than 150 and the degree of saponification is less than 20 mol%, the suspension system becomes unstable, and there are problems such as generation of coarse particles and increase of scale formation. On the other hand, the average degree of polymerization exceeds 600 and the degree of saponification is 60 mol%.
Above, the fish eye increases.

The amount of the partially saponified polyvinyl alcohol added may be appropriately adjusted in the range of 0.01 to 5 parts, preferably 0.05 to 1 part, per 100 parts (parts by weight, hereinafter the same) of the charged monomers. it can.

In the present invention, it is preferred that only the oil-soluble partially saponified polyvinyl alcohol is used as the dispersant at the start of polymerization.

However, since such an oil-soluble partially saponified polyvinyl alcohol alone cannot keep the suspension system stable over the entire period of the polymerization reaction, at the same time as the initiation of the polymerization, a suspension agent which is more water-soluble than the dispersant is used. Must be added continuously or sequentially.

Thus, the addition of the water-soluble suspending agent after the initiation of polymerization has a strong effect of protecting the monomer droplets when the above-mentioned dispersant and suspending agent are charged all at once before the initiation of polymerization. In the case of a suspension agent, the dispersibility of fish eyes is significantly impaired due to the uneven distribution before the start and the increase in the thickness of the resin skin layer.
For this reason, it is necessary to add a suspending agent according to the droplet particles that are likely to be agglomerated as the polymerization proceeds.

As such a suspending agent, any suspending agent which is more water-soluble than the above-mentioned oil-soluble partially saponified polyvinyl alcohol may be used, and particularly, the water-soluble suspending agent having an average degree of polymerization of 700 to 3000 and a degree of saponification of 70 to 85 mol%. Partially saponified polyvinyl alcohol (A) or the degree of methoxy substitution is 26 to 30% by weight,
The hydroxypropoxy substitution degree is 4 to 15% by weight, and the viscosity of a 2% by weight aqueous solution thereof at 20 ° C. is 5 to 400.
Hydroxypropylmethylcellulose (B) having a cps of 0 cps is suitable, and these suspending agents can be used alone or in combination, and when used in combination, the weight ratio is (A) / (B) = 9 / It is preferably in the range of 1 to 3/7.

Regarding the timing of addition, it is preferable to start the addition continuously or sequentially from the start of the polymerization and to finish the addition when the polymerization rate reaches 5 to 50% (preferably 10 to 40%). . Further, the addition amount is 0.03 to 0.1 part, preferably 0.04 to 0.09, relative to 100 parts of the charged monomer.
It can be appropriately adjusted within the range of parts.

In the production method of the present invention, vinyl chloride can be used alone as a monomer, or a monomer mixture containing vinyl chloride as a main component and a comonomer copolymerizable with vinyl chloride (usually It is also possible to use vinyl containing 50% by weight or more). Such comonomers include vinyl acetate, vinyl esters such as vinyl propionate, and (meth) acrylates such as methyl acrylate and ethyl acrylate.
Acrylic esters, ethylene, olefins such as propylene, maleic anhydride, acrylonitrile, styrene,
Examples thereof include vinylidene chloride.

Further, in the production method of the present invention, as the polymerization initiator, those which have been conventionally used for vinyl chloride-based polymerization can be used, and specifically, t-butylperoxy neodecanoate and t-butylperoxy are used. Pivalate, t-hexyl peroxy neodecanoate, t-hexyl neohexanoate, t-hexyl peroxy pivalate, α-cumyl peroxy neodecanoate, 2,4,4-trimethylpentyl-2-peroxy 2-Neodecaneate and other perester compounds; diisopropyl peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, dimethoxyisopropyl peroxydicarbonate, diethoxyethyl peroxydicarbonate Percarbonate compounds such as carbonates Decanoyl peroxide, benzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, 2,4-dichlorobenzoyl peroxide, p- methane hydroperoxide,
Isobutyryl peroxide, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, 3,5,5
-Peroxides such as trimethylhexanoyl peroxide and lauroyl peroxide; α, α'-azobisisobutyronitrile, α, α'-azobis (2,4-dimethylvaleronitrile), α, α'-azobis (4-METHOKI-
One of oil-soluble polymerization initiators such as azo compounds such as 2,4-dimethylvaleronitrile) can be used alone or in combination of two or more, and further, potassium persulfate, ammonium persulfate, and peroxide can be used. It can also be used in combination with a water-soluble polymerization initiator such as hydrogen.

The polymerization initiator is added during the charging of water or monomers,
Alternatively, it may be added after the completion of the preparation, and it may be prepared by uniformly mixing it with the monomer in advance and preparing it together with the monomer, or further preparing it as an aqueous emulsion together with the aqueous medium.

In the production method of the present invention, suspension polymerization is carried out under known conditions except that the above-mentioned oil-soluble partially saponified polyvinyl alcohol is used at the start of polymerization and a water-soluble suspending agent is added from the start of polymerization. It can be carried out.

For example, the amount of the aqueous medium used to suspend and disperse the polymer component of the monomer is the same as in the conventional method, and the ratio of the aqueous medium to the monomer (water / monomer) is 1. .0 to
It may be about 1.5, and water may be added during the polymerization if necessary.

Further, the amount of the polymerization initiator used, the polymerization temperature, etc. may be in the conventionally employed range, and if necessary, a polymerization degree adjusting agent, a pH adjusting agent and the like may be added to the polymerization system. .

[0023]

According to the method for producing a vinyl chloride polymer of the present invention, fisheye has high porosity, good processability, and even when kneading is made shallow by using a polymer plasticizer. It is possible to produce a high-quality vinyl chloride polymer with less generation of

[0024]

EXAMPLES Hereinafter, the present invention will be specifically shown by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples. In the following examples, parts are parts by weight.

Example 1 An autoclave having an internal volume of 2000 liters was charged with 1100 kg of deionized water and the dispersant shown in Table 1 in the amounts shown in the same table. Next, it was deaerated with a vacuum pump until the internal pressure of the autoclave reached 60 mmHg.

Then, 550 kg of vinyl chloride monomer was charged and stirring was started. Next, hot water was passed through the jacket to start the temperature rise, and 385 g of 2-ethylhexyl peroxydicarbonate was injected as a polymerization initiator by a pump (at this time, the polymerization rate was 0% at the start of polymerization).
At the same time, the suspending agents shown in Table 1 were continuously added, and the polymerization was continued at a temperature of 51 ° C. Internal pressure of autoclave is 6.5k
When the amount reached g / cm ² G, the reaction was stopped, unreacted monomers were recovered, dehydrated and dried to obtain a polymer.

The resulting polymer was prepared by the following method.
Bulk specific gravity, particle size distribution, plasticizer absorption, fish eye I,
The fish eye II was measured. The results are also shown in Table 1.
To do.Bulk specific gravity It was measured according to JIS K-6721.Particle size distribution It was measured according to JIS Z-8801.Plasticizer absorption Aluminum alloy container with inner diameter of 25 mm and depth of 85 mm
Fill the bottom of the glass fiber with glass fiber and polymerize the sample with vinyl chloride.
A body of 10 g was collected and put in. Dioctyl phthalate
Add 15cc of DOP and leave it for 30 minutes for DOP
Was thoroughly permeated into the polymer. After that, 1500G acceleration
Centrifuge excess DOP to absorb 10g of polymer
Measure the amount of DOP generated and convert to 100 g of polymer.
I calculated. Fish eye i 100 parts of sample vinyl chloride polymer, tribasic lead sulfate 1
Parts, lead stearate 1.5 parts, titanium oxide 0.2 parts, mosquito
Carbon black 0.1 parts and DOP 50 parts
Rolled mixture at 145 ° C for 1 minute each
And after kneading for 2 minutes to prepare 2 kinds of samples,
Molded into a sheet with a thickness of 0.2 mm, sheet 100 cm²
The number of fish eyes contained in each hit was counted.Fish eye II 100 parts of sample vinyl chloride polymer, carbon black
0.1 parts, Ba-Zn stabilizer 2.0 parts, epoxidized large
Soybean oil 5.0 parts and polyester polymer plasticizer PN-6
50 (brand name, manufactured by Asahi Denka) mixed at a ratio of 65 parts
The mixture was rolled at 150 ° C. for 4 minutes each and
After preparing 2 kinds of samples kneaded for 6 minutes,
Molded into a 0.3 mm sheet, 100 cm sheet²Hit
The number of fish eyes contained in was counted.

[Examples 2 to 4, Comparative Examples 1 and 2] A vinyl chloride polymer was prepared in the same manner as in Example 1 except that the dispersing agent and the suspending agent shown in Table 1 were added as shown in the same table. Was polymerized and its physical properties were measured in the same manner. The results are also shown in Table 1.

[0029]

[Table 1] (Note) <Dispersant> Oil-soluble partially saponified polyvinyl alcohol having a polymerization degree of 235 and a saponification degree of 50.7 mol% <Suspension agent> Water-soluble partially saponified polyvinyl alcohol having a polymerization degree of 2550 and a saponification degree of 80 mol% <Suspension agent > Hydroxypropyl methylcellulose having a methoxy substitution degree of 29.2% by weight and a hydroxypropoxy substitution degree of 8.9% by weight, and the viscosity of the 2% by weight aqueous solution at 20 ° C. is 49.5 cps <Suspending agent> Polymerization degree 780, Saponification degree 72.9 mol% water-soluble partially saponified polyvinyl alcohol

From the results shown in Table 1, when the dispersant and the suspending agent were charged before the start of polymerization (Comparative Example 1), the plasticizer absorbency was poor and the fish eye was relatively poor. In addition, even if the kind and the amount of the suspending agent are the same as those in Example 2, the fish eyes are extremely poor when the charging is not started from the start of polymerization (Comparative Example 2).

On the other hand, according to the polymerization method (Example) of the present invention, it is recognized that the absorbability of the plasticizer is good and the fish eyes disappear in a short kneading time.

Claims (2)

[Claims] 1. A method for producing a vinyl chloride polymer in which vinyl chloride or a monomer mixture containing vinyl chloride is suspended and dispersed in an aqueous medium to carry out suspension polymerization, wherein (1) the average degree of polymerization is 150 to Polymerization is initiated by using 0.01 to 5 parts by weight per 100 parts by weight of the charged monomer as a dispersant having a saponification degree of 600 and a partially saponified polyvinyl alcohol of 20 to 60 mol%, and (2) the partially saponified polyvinyl alcohol. A suspending agent having a higher water solubility than alcohol is continuously or sequentially added from the initiation of polymerization, and the addition is terminated when the polymerization rate reaches 5 to 50%. Production method. 2. A water-soluble partially saponified polyvinyl alcohol having an average degree of polymerization of 700 to 3000 and a degree of saponification of 70 to 85 mol% and / or a degree of methoxy substitution as a suspending agent added continuously or sequentially from the initiation of polymerization. Is 26 to 30% by weight, the degree of hydroxypropoxy substitution is 4 to 15% by weight,
And the viscosity of the 2% by weight aqueous solution at 20 ° C. is 5 to 4
The method for producing a vinyl chloride polymer according to claim 1, wherein 0.03 to 0.1 part by weight of hydroxypropylmethyl cellulose having a rate of 000 cps is used.