JP3254772B2 - Method for producing vinyl chloride polymer - Google Patents

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 having a high polymerization productivity and low fisheye, and the vinyl chloride polymer obtained by the present invention is suitable for use in soft resins. It is.

[0002]

2. Description of the Related Art Since vinyl chloride resins have excellent physical and mechanical properties, they are used for a wide range of applications in both hard resins and soft resins.

[0003] Recently, in the molding of a soft vinyl chloride resin, there is a demand to lower the molding temperature as much as possible in order to improve the weather resistance of the molded article.

[0004] As the soft vinyl chloride resin, a polymer obtained by a suspension polymerization method is usually used, and the polymer contains a hardly meltable polymer which causes fish eyes, which is a kind of defect in a molded article. Particles (hereinafter referred to as hard-to-melt particles) are included, and in molding, the generation of fish eyes is suppressed by employing molding conditions under which the hard-to-melt particles are melted. When using a vinyl chloride polymer having a high content of hardly meltable particles, it is necessary to use a high molding temperature to prevent the occurrence of the fish eyes,
As a result, there was a problem that the weather resistance of the molded article was inferior.

[0005] From the above technical background, it is possible to apply a low molding temperature in the molding field of soft vinyl chloride resin.
There is a need for a vinyl chloride polymer having a low content of hardly meltable particles.

[0006] Conventionally, as a method for producing a vinyl chloride-based polymer having low fisheye formation and high polymerization stability,
Highly partially saponified polyvinyl alcohol having a saponification degree of 65 to 75 mol%, low partially saponified polyvinyl alcohol having a saponification degree of 35 to 45 mol%, and a methoxy group content of 28
A method in which methylhydroxypropylcellulose having a hydroxyl group content of 7 to 12% and a hydroxy group content of 7 to 12 is used (Japanese Patent Application Laid-Open No.
JP-A-152703) and average particles of 0.1 to 10 μm
Polymerization in the presence of a vinyl chloride-based paste resin (JP-A-61-190542) or a saponification degree of 6
A method in which 5 to 75 mol% of partially quenched polyvinyl alcohol and 50 to 80% of hydroxypropoxy cellulose are used in combination with nohydroxypropylcellulose
No. 275606) are known, but none of these methods has sufficiently improved fisheye.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a vinyl chloride-based polymer in which the content of hardly-fusible particles is low and most of the polymer particles are occupied by porous and excellent plasticizer-absorbing particles. It is intended to provide a manufacturing method.

[0008]

As a result of intensive studies to solve the above problems, the present inventors have found that aqueous suspension polymerization of vinyl chloride polymers has different saponification degrees.
The present inventors have found that the above object can be achieved by using various kinds of polyvinyl alcohol as a dispersant and controlling the amount of water added during the polymerization, thereby completing the present invention.

[0009] That is, the present invention provides a method of manufacturing vinyl chloride polymer to produce a vinyl chloride polymer of vinyl chloride monomer to suspension polymerization in an aqueous medium, is (A) a saponification degree of 78 ~ 82 mol%, and 4
The viscosity of the aqueous solution at 20 ° C. is 30 to 50 cps.
And (B) a saponification degree of 45 to 51 mol%, and 10% by weight thereof in a 1: 1 water-methanol mixed solvent at a volume ratio of
Viscosity at 20 ° C. of the aqueous solution using the dispersing agent comprising a polyvinyl alcohol which is 7～23Cps, if the
The amount of the polyvinyl alcohol used in (A) is vinyl chloride.
0.05-0.03 weight per 100 weight parts of monomer
And the amount of polyvinyl alcohol used in (B) is salt
0.15 to 0.0 per 100 parts by weight of vinyl chloride monomer
5 parts by weight, and the polymerization conversion rate by adding to the polymerization system an amount of water not exceeding the volume reduction of P caused suspension during the polymerization the polymerization proceeded at once or divided 50-70
%, The volume of the suspension is 98-102% of the volume of the suspension before the start of polymerization , and the polymerization conversion rate exceeds 70%.
After the point of time , the polymerization is continued without adding water to the polymerization system .

In the present specification, the degree of saponification of polyvinyl alcohol is determined according to the polyvinyl alcohol test method of JIS K6726, and is determined in accordance with the following JIS test.

(5. Test method of JIS K6726)
5.2 ) Degree of saponification 5.2.1 Reagent The reagent is as follows. (1) N / 5, N / 10 sodium hydroxide solution JIS
K8576 [sodium hydroxide (reagent)] is used for the adjustment and the standardization ⁽¹⁾ is performed. (2) N / 5, N / 10 sulfuric acid Prepared as a primary grade of JIS K8951 [sulfuric acid (reagent)]. (3) Phenolphthalein JIS K8006 (basic matters regarding standardization during the test of the content of the reagent) Prepared by (4) Sulfamic acid Sulfamic acid according to JIS K8005 (standard reagent for volumetric analysis). (5) Bromthymol blue JIS K8006 3. Prepared by Note ⁽¹⁾ Standardization of N / 10 sodium hydroxide solution Accurately weigh 2 to 2.5 g of the dried sulfamic acid in a desiccator and add water to make 250 ml. This solution 25
Use ml to standardize bromthymol blue as the indicator.

5.2.2 Apparatus The apparatus is as follows. (1) 300 ml Erlenmeyer flask with co-threading (2) 50 ml buret, 0.1 ml minimum scale (3) 25 ml whole bipet (4) Chemical balance Capacity 100-200 g, sensitivity 1
mg

5.2.3 Operation (A) In the case of a saponification degree of 97 mol (%) or more: about 3 parts of the original sample
g in a Erlenmeyer flask with a co-senser, and add about 10
0 ml was added and dissolved by heating. After cooling, 25 ml of N / 10 sodium hydroxide solution was added, and the mixture was allowed to stand at room temperature for 2 hours or more. Next, 25 ml of N / 10 sulfuric acid was added, and excess sulfuric acid was
Titrate with a / 10 sodium hydroxide solution using phenolphthalein as an indicator until a slight red color is exhibited, and set the titer to aml. Separately, a blank test was performed, and the titer of the N / 10 sodium hydroxide solution required for the blank test was set to bml,
Next, it is calculated to two decimal places by the formula, and the mass (%) of the residual acetic acid group and the mole (%) of the saponification degree with respect to the pure content are calculated. Where A: mass of residual acetate groups (%) B: mol of residual acetate groups (%) C: degree of saponification degree (%) s: mass of original sample (g) P: pure content (%) F: N / 10 titer of sodium hydroxide solution

(B) When the saponification degree is less than 97 mol (%): About 0.5 g of the original sample is accurately weighed into a conical flask equipped with a co-extruder, dissolved by heating with about 100 ml of water, and cooled.
25 ml of a / 5 sodium hydroxide solution is added, and the mixture is allowed to stand at room temperature for 2 hours or more. Next, 25 ml of N / 5 sulfuric acid is added, and the excess sulfuric acid is titrated with a N / 10 sodium hydroxide solution using phenolphthalein as an indicator until it shows a faint red color.
Separately, a blank test is performed, and the value is calculated to two decimal places by the formula of 5.2.3 (A), and the saponification degree mole (%) is calculated.

In the present specification, the viscosity of polyvinyl alcohol is determined according to the polyvinyl alcohol test method of JIS K6726 and determined in accordance with the following JIS test.

("5. Test method" of JIS K6726
5.8 Viscosity 5.8.1 Instrument The instrument is as follows. (1) Erlenmeyer flask 500ml (2) Viscometer ⁽¹⁾ Synchronous electric rotary viscometer (3) Ueizakara Capacity 100-200g, Sensitivity 0.1g (4) Constant temperature water tank Note ⁽¹⁾ JIS K2807 ( A Ubbelohde viscometer 1A or a Heppler viscometer specified in a capillary kinematic viscosity tester for petroleum products) may be used.

5.8.2 Operation 3 parts each of 12 g of the original sample
Individual pieces are weighed with a balance and placed in an Erlenmeyer flask.

The predetermined density (3.8.4.0) is calculated by the following equation.
And 4.2%) and left for 30 minutes. Here W _a: amount of water added (ml) R: Volatiles (%) C _1: the concentration of the predetermined solution (%)

Next, heating and dissolving while stirring in a hot water bath ⁽¹⁾
I do. This is cooled to near room temperature, put in a constant temperature water tank of 20 ± 0.1 ° C., and the temperature of the test solution is raised to 20 ° C. and completely removed.

Next, the viscosity at 20 ± 0.1 ° C. was measured using a viscometer, expressed in centiboise, and at the same time, the concentration ⁽²⁾
Is measured.

The vertical axis of the graph represents the viscosity, and the horizontal axis represents the measured concentration (%), and a relation curve is drawn to obtain a 4% viscosity (cP) (P
a · s) is calculated to one digit after the decimal point ⁽³⁾ . Note ^{(1) When the} saponification degree is 97 mol (%) or more, the liquid temperature is 95 ~
When the saponification degree is less than 97 mol (%), the liquid temperature is 78 to 81 ° C. for 2 hours. Note ⁽²⁾ Concentration measurement Approximately 5 g of the test solution is accurately weighed with a chemical balance into a weighing bottle whose mass is known in advance, evaporated to dryness without burning, dried at 105 ± 2 ° C until constant weight, and placed in a desiccator. , And weigh the mass to determine the concentration (%). Here, _Cm : Concentration (%) r: Residue (g) a: Mass of test solution (g) Note ^{(3) When} expressing viscosity, always use the viscosity meter used. In the case of a rotary viscometer, the roak and the number of rotations shall be added. However, the conversion rate of Pa · s is 1 cP = 10
^-3 Pa · s.

The present invention will be described below in more detail. In the method of the present invention, (A) a specific highly partially saponified polyvinyl alcohol and (B) a specific low partially saponified polyvinyl alcohol are used in combination as dispersants. I do.

Hereinafter, this will be described in more detail.
In the method of the present invention, two kinds of partially saponified polyvinyl alcohols described below are used in combination as a dispersant.

The above (A) used in the present invention
Has a saponification degree of 78 to 82 mol% and a 4% by weight aqueous solution having a viscosity at 20 ° C. of 3%.
The viscosity is from 0 to 50 cps , and more preferably the viscosity is from 37 to 45 cps . The amount used is
It is 0.05 to 0.03 parts by weight per 100 parts by weight of the phenyl-based monomer . When the amount of (A) exceeds this range , the occurrence of flash eyes tends to increase, while when the amount is less than this range , the polymerization stability tends to decrease.

The polyvinyl alcohol of the above (B) has a saponification degree of 45 to 51 mol%, and has a volume ratio of 1: 1 water-methanol mixed solvent at 20 ° C. in a 10% by weight aqueous solution. The viscosity is 7-23 cps,
More preferably, the viscosity is 7 to 10 cps . The amount used is 100 parts by weight of vinyl chloride monomer.
0.15 to 0.05 parts by weight. This is the amount of (B)
Exceeds the range , the occurrence of flash eyes tends to increase, while when it is below this range , the polymerization stability tends to decrease.

The total amount of polyvinyl alcohol added is 0.
It is preferably from 0.5 to 0.30% by weight.

Any known dispersant other than the above may be used in combination as the dispersant. Dispersants that can be used in combination
Polyvinyl alcohol having a saponification degree of 85 mol% or more, partially saponified polyvinyl alcohol such as polyvinyl alcohol having a saponification degree of 55 to 70 mol%, methyl cellulose,
Hydroxypropylcellulose, water-soluble cellulose ethers such as methylhydroxypropylcellulose, acrylic acid copolymer, maleic anhydride copolymer, gelatin,
Protective colloidal polymer compounds such as starch, natural polymer compounds, esters of higher fatty acids and polyhydric alcohols, nonionic surfactants such as polyoxyethylene derivatives, metal salts of higher fatty acids, higher alcohol sulfates Anionic surfactants such as alkali salts of esters and the like can be mentioned.

In the practice of the present invention, the ratio of water / charged vinyl chloride monomer at the start of polymerization is 1.0 to 1.
7, more preferably 1.1 to 1.
5

If the ratio of water / charged vinyl chloride monomer at the start of polymerization is less than 1.0, the polymerization becomes unstable, and the resulting vinyl chloride resin particles become non-uniform.
Water / charged vinyl chloride monomer at the start of polymerization
If it exceeds 7, the polymerization can be performed stably, but the amount of the vinyl chloride-based monomer charged at the start of the polymerization is reduced, so that the productivity is lowered.

After the initiation of the polymerization, the volume of the suspension of the polymerization system decreases with the progress of the polymerization. In the present invention, the polymerization conversion reaches 50 to 70%, more preferably 55 to 65%. Water needs to be added to the polymerization system so that the volume of the suspension at the time point is the same as the volume of the suspension before the start of polymerization.

The method of adding water may be batch or divided.
The time of addition is such that the polymerization conversion rate is 50 to 70% after the start of the polymerization.
May be added at any time during the period up to the point where the amount of the suspension must be such that the volume of the suspension at the time of addition does not exceed the volume of the suspension before the start of polymerization. When the rate reaches 50 to 70%, the volume of the suspension is substantially the same as the volume of the suspension before the start of the polymerization, specifically, 98 to 90% of the volume of the suspension before the start of the polymerization. It is necessary to add an amount of water so as to be about 102%. The amount of water added
If it exceeds 102%, scale adhesion tends to occur in the polymerization vessel, while if it is less than 98%, the removal of heat of polymerization becomes insufficient and many fish eyes are generated.

As described above, in the present invention, by adding an amount of water which does not exceed the volume reduction amount of the suspension produced during the polymerization during the polymerization, the latter half of the polymerization, that is, the polymerization conversion rate of 50 to 70% is achieved. The polymerization after the time can be stably performed, and as a result, the amount of hardly meltable particles generated in the latter half to the last half of the polymerization is extremely small.

In the present invention, the polymerization conversion rate exceeds 70%.
After that point, the polymerization is started without adding water to the polymerization system.
Let it continue. When the polymerization conversion rate exceeds 70%, even if the amount of the suspension of the polymerization system is adjusted, the next period is too late, and only a polymer having a lot of flash eyes can be obtained due to generation of hardly soluble particles.

On the other hand, when the polymerization conversion is less than 50%,
Even if the amount of the suspension of the polymerization system is adjusted to the same amount as the amount of the suspension before the start of the polymerization, when the above-mentioned state is not maintained when the polymerization conversion reaches 50%, fish Only a polymer with many eyes can be obtained.

The decrease in the volume of the suspension of the polymerization system can be calculated by the following equation, in which the relationship between the time and the polymerization conversion rate is determined in advance by experiments. Volume decrease (ΔV) = (Amount of monomer charged) × (Conversion rate) ×
[(1 / monomer density)-(1 / 1.4)]

In the present invention, various radical polymerization catalysts can be used as the polymerization catalyst. For example, a known oil-soluble radical catalyst is used. Catalysts that can be preferably used include, for example, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, tertiary butyl peroxynedecanoate, di (2-ethoxyethyl) peroxydicarbonate, tertiary hexyl peroxy neohexano. Organic peroxides such as acetate, isobutyryl peroxide, cumyl peroxy neodecanoate, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 2, An azo compound such as 2'-azobis-4-methoxy-2,4-dimethylvaleronitrile or a combination thereof.

In the present invention, the total amount of the polymerization catalyst added is
0.02 to 100 parts by weight per 100 parts by weight of the vinyl chloride monomer.
The amount is preferably 20 parts by weight, and more preferably 0.03 to 0.1 part by weight.
15 parts by weight.

In the present invention, other additives can be optionally used within a range not to impair the object of the present invention. Examples of such additives include alcohols, fatty acids, esters, and buffers.

In the present invention, the vinyl chloride monomer is
Vinyl chloride monomer itself, or a monomer copolymerizable therewith, such as ethylene, propylene, vinyl acetate, alkyl vinyl ether, acrylic acid or methacrylic acid and esters thereof, maleic acid Or a monomer mixture such as fumaric acid and its ester acid. When using a monomer mixture,
It is preferable that the comonomer coexist within a range not exceeding 15% by weight based on vinyl chloride.

In carrying out the present invention, the polymerization reaction temperature is 40
The range of -70 ° C is preferred. The polymerization time is 7 to 10
Time is appropriate.

[0041]

According to the present invention, it is possible to obtain a vinyl chloride polymer powder which enables stable polymerization and has a good particle size distribution. In addition, the polymer powder is composed of particles having a porous shape and excellent plasticizer absorption, and contains only a small amount of hardly meltable particles having poor heat melting properties.

Therefore, the vinyl chloride polymer according to the present invention is extremely suitable for a soft vinyl chloride resin, and adopts molding conditions that generate many fish eyes when a conventional vinyl chloride suspension polymer is used. Even so, according to the polymer of the present invention, it is possible to obtain a soft vinyl chloride resin molded article having extremely few fish eyes.

[0043]

The present invention will be described more specifically with reference to the following examples.

In the following examples, the particle size distribution, the polymerization conversion ratio with respect to the polymerization time and the fish eye were measured by the following methods.

Measurement method of particle size distribution: Measured by sieve shaking

Method for measuring polymerization conversion: 2800 g of deionized water, 0.7 g of polyvinyl alcohol having a saponification degree of 78 to 82 mol%, and polyvinyl alcohol having a saponification degree of 45 to 51 mol% in an autoclave having an internal volume of 5 liters. 2.
4 g, cumyl peroxy neodecanoate 0.3 g, di (2-ethoxyethyl) peroxy dicarbonate 0.1 g.
4 g and tertiary hexyl peroxy neodecanoate 0.9 g were charged, and air in the autoclave was removed by a vacuum pump. After that, vinyl chloride monomer 1750
The polymerization was started at 51 ° C. with stirring. The polymerization was stopped every hour after the start of the polymerization, the weight of the vinyl chloride resin at that time was measured, the conversion was calculated, and the relationship between the polymerization time and the conversion was obtained. The results are as shown in FIG. The polymerization conditions employed in the following Examples 1 to 3 and Comparative Example 1 are basically the same as the above polymerization conditions.

Measurement method of fish eye: 100 parts by weight of each vinyl chloride polymer obtained in each example, 50 parts by weight of trimellit plasticizer, 5 parts by weight of dibasic lead, and 1 part by weight of lead stearate were mixed. After that, 8 inch diameter 19 / 21r
pm and heated to 170 ° C. to produce 0.5 mm
At a roll interval of 4 minutes to form a sheet. Thereafter, the number of fish eyes existing in the area of 10 cm × 10 cm is counted.

Example 1 Deionized water 280 was placed in an autoclave having an internal volume of 5 liters.
0 g, 0.7 g of polyvinyl alcohol having a saponification degree of 78 to 82 mol%, 2.4 g of polyvinyl alcohol having a saponification degree of 45 to 51 mol%, 0.3 g of cumyl peroxy neodecanoate, di (2-ethoxy) Ethyl) peroxy dicarbonate 0.4 g and tertiary hexyl peroxy neodecanoate 0.9 g were charged, and the air in the autoclave was removed by a vacuum pump. Thereafter, 1750 g of a vinyl chloride monomer was charged, and polymerization was started at 51 ° C. with stirring. Two hours, three hours, 3.5 hours, four hours, and five hours after the start of the polymerization, 100 g of deionized water was injected under pressure. Thereafter, the polymerization was continued under the same conditions. Eight hours after the start of the polymerization, the pressure inside the autoclave was reduced by ² kg / cm ² , so the polymerization reaction was stopped.

Example 2 3 hours and 5 hours after the start of the polymerization, 2 parts of deionized water were added.
50 g was injected at a time. Otherwise, polymerization was performed under the same conditions as in Example 1.

Example 3 3.5 hours after the start of polymerization, 200 g of deionized water and a further 4 g
Time, 4.5 hours, 5 hours, 10 deionized water respectively
0 g was injected at a time. Otherwise, polymerization was performed under the same conditions as in Example 1.

Comparative Example 1 Polymerization was carried out under the same conditions as in Example 1 except that no water injection was performed.

Evaluation of Examples 1 to 3 and Comparative Example 1 For the polymerization products obtained in Examples 1 to 3 and Comparative Examples 1 to 3, the yield and the particle size distribution, polymerization stability, And the evaluation of fish eye was measured.
Table 1 shows the results.

As can be understood from Table 1, the vinyl chloride particles obtained in Examples 1 to 80 have a particle size in the range of 120 to 200 M, 80% or more, and the degree of uniformity of the particle size is small. It is clear that the polymerization was stable. In addition, fish eyes were less likely to occur. The polymerization stability was also good.

On the other hand, it can be seen that Comparative Example 1 had a wide particle size distribution and poor polymerization stability. The fisheye evaluation was also low, which was not preferable.

[0055]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between polymerization time and conversion under the polymerization conditions employed in Examples 1 to 3 and Comparative Example 1.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Hiroshi Minemura 1-1-1, Funami-cho, Minato-ku, Nagoya-city, Aichi Prefecture Inside Nagoya Research Laboratory, Toagosei Chemical Industry Co., Ltd. (72) Inventor Naori Asada, Funami, Minato-ku, Nagoya-shi, Aichi Prefecture Nagoya Research Institute, Toagosei Chemical Industry Co., Ltd. (72) Inventor Yoshito Fujiki 1 to 1, Funamicho, Minato-ku, Nagoya City, Aichi Prefecture Toagosei Chemical Industry Co., Ltd. Nagoya Research Institute (56) JP-A-53-136089 (JP, A) JP-A-59-38212 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 2/00-2/60

Claims (1)

(57) [Claims] 1. A process for producing a vinyl chloride polymer, which comprises subjecting a vinyl chloride monomer to suspension polymerization in an aqueous medium to produce a vinyl chloride polymer, wherein (A) the saponification degree is 78 to 82 mol. % And 4
The viscosity of the aqueous solution at 20 ° C. is 30 to 50 cps.
And (B) a saponification degree of 45 to 51 mol%, and 10% by weight thereof in a 1: 1 water-methanol mixed solvent at a volume ratio of
Viscosity at 20 ° C. of the aqueous solution using the dispersing agent comprising a polyvinyl alcohol which is 7～23Cps, if the
The amount of the polyvinyl alcohol used in (A) is vinyl chloride.
0.05-0.03 weight per 100 weight parts of monomer
And the amount of polyvinyl alcohol used in (B) is salt
0.15 to 0.0 per 100 parts by weight of vinyl chloride monomer
By adding water in an amount of 5 parts by weight and not exceeding the volume reduction amount of the suspension produced during the polymerization during the polymerization to the polymerization system in a lump or in a divided manner, the polymerization conversion rate becomes 50 to 70%. The volume of the suspension when reached is 98 to 10 of the volume of the suspension before the start of polymerization.
2%, and after the polymerization conversion rate exceeds 70%,
A method for producing a vinyl chloride polymer, wherein polymerization is continued without adding water to the system.