JPH09110906A - Production of vinyl chloride polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a process for producing a vinyl chloride polymer which requires low torque when it gels and melts in a molding process and can give a molded item with good luster. SOLUTION: In producing a vinyl chloride polymer by polymerizing a monomer component comprising vinyl chloride or a mixture mainly comprising vinyl chloride in an aq. medium, a cross-linker in an amt. of 0.01-2wt.% of the monomer component is used and the net stirring power from the initiation of polymn. to a conversion of 10% is controlled to 0.5-3kW/m<3> .

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method for producing a vinyl chloride polymer. More specifically, the present invention relates to a method for producing a vinyl chloride polymer having a low torque when the polymer gels during processing and molding.

[0002]

BACKGROUND OF THE INVENTION Vinyl chloride-based polymers are vinyl chloride monomers or mixtures of copolymerizable monomers mainly composed of vinyl chloride monomers (hereinafter, these are collectively referred to as "vinyl chloride-based monomers"). "Polymer", and the polymer obtained by polymerizing this is referred to as "vinyl chloride polymer".) In the presence of a polymerization initiator, suspension polymerization or emulsification in an aqueous medium containing a dispersant or an emulsifier. Manufactured by polymerization.

Processability and moldability of vinyl chloride resins, which are generally vinyl chloride polymers (molded product quality, extrusion productivity)
Depends on the particle shape, the aggregated state of the primary particles, and the like. In the suspension polymerization method, various attempts have been made to improve productivity during processing, such as increasing the bulk density of the vinyl chloride-based monomer to increase the discharge amount during extrusion molding. Furthermore, in recent years, it has become possible to further increase the discharge rate of the extruder by adopting a new type extruder such as a conical different direction extruder.

[0004]

However, when it is attempted to increase the discharge amount at the time of extrusion by improving the vinyl chloride polymer or improving the extrusion molding machine as described above, that is, the productivity of extrusion processing is improved. In such a case, the ejection torque increases due to the increase in the discharge amount, and finally, the phenomenon that the limit of the motor load of the extruder dominates the limit of the extrusion discharge amount occurs. In order to prevent such a phenomenon, a vinyl chloride polymer capable of maintaining a low torque during processing and molding has been demanded.

The present inventors have already reported that when the average degree of polymerization is the same,
The vinyl chloride-based polymer obtained by adding a cross-linking agent when polymerizing the vinyl chloride-based monomer has a torque at the time of gelation and melting more than the vinyl chloride-based polymer without the cross-linking agent added. It has been found that the product becomes low, but when a pipe is molded using the vinyl chloride polymer obtained in this way, the phenomenon that the luster (gloss) of the appearance of the pipe deteriorates occurs, resulting in a good product. It was not possible to obtain.

[0006]

Means for Solving the Problems In view of the above situation, the present inventors have made extensive studies and as a result, when a vinyl chloride monomer is allowed to undergo a polymerization reaction in an aqueous medium together with a crosslinking agent, a specific amount of crosslinking occurs. It has been found that the problem can be solved by using an agent and controlling the net stirring power within a specific range from the start of the reaction to a specific reaction conversion rate.

That is, the gist of the present invention is that when a vinyl chloride-based monomer is polymerized in an aqueous medium to produce a vinyl chloride-based polymer, a crosslinking agent is added to 100 parts by weight of the vinyl chloride-based monomer. 01 to 2 parts by weight and a net stirring power of 0.5 to 3 kW from the initiation of polymerization to a reaction conversion rate of 10%.
The method for producing a vinyl chloride-based polymer is characterized in that it is controlled in the range of / m ³ .

Another object of the present invention is to provide a method for producing the above vinyl chloride-based polymer using a diallyl ester and / or triallyl ester of a polyvalent organic acid as a cross-linking agent, and a produced vinyl chloride-based polymer. The average degree of polymerization of the coalescence is 50
The above method for producing a vinyl chloride polymer is 0 or more and 1500 or less.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. <Raw material> Monomer: The vinyl chloride monomer used in the method of the present invention is, as described above, a mixture of vinyl chloride monomer alone and a copolymerizable monomer mainly containing vinyl chloride monomer. including. As the other monomer copolymerizable with the vinyl chloride monomer, those conventionally used in the polymerization of vinyl chloride monomer may be used without any particular limitation.

Examples of the above-mentioned other monomers include vinyl esters such as vinyl acetate and vinyl propionate, alkyl vinyl ethers such as octyl vinyl ether and cetyl vinyl ether, α-olefins such as ethylene and propylene, and methyl acrylate. , (Meth) acrylic acid alkyl esters such as methyl methacrylate, or vinylidene compounds such as vinylidene chloride.
These other monomers are usually 2
Used at a rate of 0% or less. Dispersant: The dispersant used in the method of the present invention may be one that is usually used in the suspension polymerization method of vinyl chloride monomer and is not particularly limited.

Examples thereof include partially saponified polyvinyl acetate (so-called polyvinyl alcohol), cellulose derivatives such as hydroxypropylmethyl cellulose, and water-soluble polymers such as gelatin. Further, as a dispersion aid, an anionic surfactant such as sodium lauryl sulfate, a nonionic surfactant such as sorbitan fatty acid ester or glycerin fatty acid ester may be used.

These dispersants and dispersion aids can be used alone or in combination. The amount of these dispersants used is not particularly limited, and its type, polymerization temperature, type and composition of other monomers to be copolymerized with the vinyl chloride monomer, and the intended vinyl chloride-based polymer. It may be adjusted depending on the particle size and the like. Generally, 0.001 to 2% by weight, preferably 0.03 to
Used within the range of 1% by weight.

Polymerization initiator: The polymerization initiator that can be used in the method of the present invention is not particularly limited and may be one that is generally used in the suspension polymerization method of vinyl chloride monomer. For example, t-butyl peroxypivalate, t-butyl peroxy neodecanoate, t-hexyl peroxypivalate, t-hexyl peroxy neodecanoate, α
-Perester compounds such as cumyl peroxy neodecanoate, peroxide compounds such as dilauroyl peroxide, diisopropyl peroxydicarbonate,
Examples thereof include percarbonate compounds such as di-2-ethylhexyl peroxydicarbonate, azo compounds such as azobis (2,4-dimethylvaleronitrile) and azobisisobutyronitrile. These polymerization initiators can be used alone or in combination of two or more.
Although the amount of the polymerization initiator used varies depending on the type of the initiator, the polymerization temperature, the desired reaction time, etc., it is generally in the range of 0.01 to 1% by weight based on the total amount of the vinyl chloride monomer. Chain transfer agent: A chain transfer agent may be used in combination in the polymerization reaction of the present invention.

As the chain transfer agent, various commonly used ones such as trichloroethylene, 2-mercaptoethanol, 2-pentene, isopropyl alcohol and the like can be used. The timing and method of adding these chain transfer agents are not particularly limited, and they may be added all at once or continuously in the polymerization system before the initiation of polymerization or during the polymerization reaction.

Cross-linking agent: The cross-linking agent used in the method of the present invention means a cross-linking structure having two or more ethylenically unsaturated double bonds in the molecule during the polymerization of vinyl chloride monomer. Refers to monomers that can be formed. The type thereof may be one conventionally used in the suspension polymerization method of vinyl chloride monomer and is not particularly limited, and examples thereof include diallyl phthalate, diallyl malate, diallyl succinate, triallyl cyanurate, and triaryl cyanurate. Allyl esters of polyvalent organic acids such as allyl isocyanurate, (meth) acrylic acid esters of polyhydric alcohols such as polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, bisphenol A modified dimethacrylate, trimethylolpropane triacrylate,
Alternatively, divinylbenzene or the like may be used.

Among these, diallyl esters and triallyl esters of polyvalent organic acids such as diallyl phthalate and triallyl isocyanurate have moderate reactivity with vinyl chloride monomers, and the crosslinking reaction can be easily controlled. For the purpose of. These cross-linking agents can be used alone or in combination of two or more. The total amount of these crosslinking agents added varies slightly depending on the crosslinking efficiency of the crosslinking agent and the average degree of polymerization of the target product, but is 0.01 to 2% by weight relative to the total amount of vinyl chloride monomer. , Preferably 0.05 to 0.5
It is desirable to use within the range of weight%.

If the amount of the cross-linking agent added is less than 0.01% by weight, the effect of the present invention of lowering the torque at the time of gelation cannot be sufficiently exerted, while if it is used in excess of 2% by weight, it is The luster tends to be too faint, which is not preferable for the purpose of the present invention. Other auxiliaries: Further, in the method of the present invention, if necessary, various polymerization auxiliaries such as an antioxidant, a pH adjuster, and a scale adhesion preventive agent used for the polymerization of vinyl chloride-based monomers may be added. It can be used as appropriate, and the addition amount and addition method of each of these components may be the general conditions conventionally used for polymerization of vinyl chloride monomers.

<Polymerization conditions> Stirring power: In the present invention, the net stirring power from the initiation of the polymerization reaction to the reaction conversion rate of 10% is 0.5 to 3.0 kW.
It is necessary to control in the range of / m ³ . Here, the “net stirring power” is the stirring power per 1 m ³ of the internal volume of the polymerization vessel, which does not include the loss (so-called “mechanical loss”) in the speed reduction mechanism section, the shaft sealing section and the like. In order to control the stirring power of the polymerizer, an empirical formula or a diagram showing the relationship between the Reynolds number Re and the power number Np of the stirring system for stirring devices of various shapes is used, or under certain stirring conditions. The Np as an apparatus constant can be experimentally obtained by actually measuring the power in step (1), and the stirring power can be controlled by adjusting the stirring rotation speed using the following formula.

The Reynolds number Re and the power number Np are the density of the contents of the polymerization vessel ρ (kg / m ³ ), the blade length d (m), the viscosity coefficient μ (kg / m · s), and the stirring blade. Is n (1 / s), the power conversion coefficient is gc (kg ・ m / kg ・ s ² ), and the stirring power that does not include loss in the speed reduction mechanism and shaft seal part is P (kg / m ・ s). s),

[0020]

## EQU1 ## Re = ρnd ² / μ

[0021]

[Number 2] because they are defined by ^{Np = Pgc / ρn 3 d 5} , the amount of liquid in the polymerization vessel V (m ³⁾ Tosureba per unit volume of the polymerization vessel net stirring power Pv (kW / m ³⁾ Is

[0022]

Equation 3] represented by ^{Pv = Npρn 3 d 5 / 102Vgc} .

That is, the net stirring power is 3 times the rotation speed of the stirring blade.
Since it is proportional to the power, the rotational speed control is the simplest for the adjustment. When the net stirring power from the start of the reaction to the reaction conversion rate of 10% is less than 0.5 kW / m ³ ,
The gloss of the appearance of the molded product tends to deteriorate. If the net stirring power during this period is larger than 3 kW / m ³ , the effect of the present invention that the torque during molding is lowered becomes insufficient.

<Polymerization / Drying Method, Apparatus> When carrying out the method of the present invention, the ratio of charging the aqueous medium, the dispersant, the polymerization initiator and various polymerization aids to the polymerization vessel, and the charging method are not particularly limited. The shape of the stirring blades, baffles, etc., which are the auxiliary equipment of the polymerization vessel used in the method of the present invention, is not particularly limited, and the equipment / equipment generally adopted conventionally can be used.

In the present invention, the start of the polymerization means the time when the reaction mixture reaches a predetermined reaction temperature, and the end of the polymerization means the time when the reaction progresses to reach the predetermined reaction conversion rate (usually the reaction). The operation is performed when the internal pressure of the polymerization vessel drops by a predetermined pressure from the saturated vapor pressure of the vinyl chloride-based monomer at a temperature). Examples of the method for terminating the polymerization in the method of the present invention include a method of adding a so-called polymerization inhibitor and a polymerization terminator, and a method of recovering an unreacted monomer from a polymerization vessel.

In order to dehydrate / dry the produced vinyl chloride polymer slurry, conventional dehydration / drying means such as centrifugal dehydration-fluid drying can be used. To remove residual vinyl chloride from the vinyl chloride polymer, a generally used method may be applied. The vinyl chloride polymer obtained by the present invention can easily remove residual monomers. Is

<Vinyl Chloride Polymer> The vinyl chloride polymer produced by the method of the present invention has an average degree of polymerization of 500.
It is preferably not less than 1500 and not more than 1500. If the average degree of polymerization is less than 500, the physical properties (mechanical strength, etc.) of the molded article using this vinyl chloride polymer tend to be insufficient, while 1
When it exceeds 500, the gloss of the surface of the obtained molded product tends to be too faint.

The content of the gel component insoluble in tetrahydrofuran in this polymer is preferably 5% by weight or less, more preferably 2% by weight or less. When the gel content exceeds 5% by weight, the gloss of the surface of the molded article tends to be too faint. The above average degree of polymerization and gel content can be generally adjusted by the kind and amount of crosslinking agent, the timing of addition, the polymerization temperature and the like.

<Molding / Processing> The vinyl chloride polymer produced by the method of the present invention can be manufactured by extrusion molding, injection molding,
It can be applied to various molding / processing methods such as a calender molding method and a vacuum molding method. Among them, it can be particularly preferably used in the extrusion molding method by taking advantage of the low torque at the time of gelation. The torque referred to herein means a rotational force required by the agitator / mixer for gelling / melting the powdery vinyl chloride polymer. The smaller this value, the larger the amount of vinyl chloride polymer that can be treated with less energy.

[0030]

EXAMPLES Next, the specific contents of the method of the present invention will be explained using examples, but the present invention is not limited as long as the gist thereof is not exceeded.
It is not limited by the following examples. <Physical property measuring method> The physical properties of the obtained vinyl chloride polymer were evaluated by the following physical property measuring methods. Average degree of polymerization Determined according to the method described in JIS K6721.

Pipe Extrusion Molding Vinyl chloride polymer 100 parts by weight Lead stearate 1.5 parts by weight Dibasic lead stearate 0.5 parts by weight Calcium stearate 0.2 parts by weight Stearic acid 0.5 parts by weight Extrusion molding Conditions Twin-screw extruder (RC100VII type manufactured by Ikegai Tekko Co., Ltd.) Cylinder temperature 150 to 170 ° C Die temperature 175 to 190 ° C Screw rotation speed 25 rpm Extrusion speed 100 kg / h

The surface condition of the molded article obtained with gloss was visually observed and the following criteria were used for the judgment criteria: Smooth and good gloss ○ The surface is smooth but the gloss is slightly inferior. △ Surface roughness is conspicuous The gloss has disappeared ×

<Examples 1 to 4> In a stainless steel polymerization vessel equipped with a stirrer and a jacket having an internal volume of 400 liters, 150 kg of deionized water and 55 parts of partially saponified polyvinyl acetate were added.
g, and the type and amount of the crosslinking agent shown in the table were charged, and the mixture was degassed by suction with a vacuum pump. Then vinyl chloride monomer 100
Then, 30 kg of a polymerization initiator (dioctyl peroxydicarbonate) was charged, and the polymerization reaction was carried out at the reaction temperature and the net stirring power shown in the table.

After the reaction was completed at a predetermined polymerization conversion rate and the vinyl chloride monomer in the polymerization vessel was recovered to atmospheric pressure, the inside of the polymerization vessel was vacuumed to remove the vinyl chloride monomer. After taking out the polymer slurry after removing the monomers and centrifugally dehydrating,
Dried. The physical properties of the vinyl chloride polymer thus obtained were evaluated as described above. The results are also shown in the table.

<Comparative Example 1> Charge was carried out in the same manner as in the above Example except that no crosslinking agent was used, and post-treatments such as polymerization and monomer removal / drying were carried out under the conditions shown in the table. . The physical properties of the obtained vinyl chloride polymer were evaluated in the same manner, and the results are also shown in the table.

<Comparative Examples 2 and 3> Obtained by conducting charging, polymerization and post-treatment under the conditions shown in the table in the same manner as in the above Examples except that the net stirring power was out of the range of the present invention. The physical properties of the vinyl chloride polymer were evaluated. The results are shown in the table.

Comparative Example 4 Physical properties (pipe extrusion molding, gloss evaluation) were carried out using a commercially available high bulk density vinyl chloride polymer. The results are shown in the table.

[0038]

[Table 1] Unit: Cross-linking agent addition amount: parts by weight Net stirring power: kW / m ³ Bulk density: g / ml Extrusion torque: kg · m Cross-linking agent · Type; DAP: Diallyl phthalate TAIC: Triallyl isocyanurate Net stirring power・ ・ ・ ・ ・ Value from polymerization start to polymerization conversion of 10%

[0039]

Industrial Applicability According to the present invention, it is possible to produce a vinyl chloride polymer which has a low torque during molding and processing such as extrusion molding, and which can give good gloss to the resulting molded article.

Claims (3)

[Claims] 1. An aqueous medium comprising a vinyl chloride monomer or a mixture of copolymerizable monomers mainly composed of vinyl chloride monomer (hereinafter, these are collectively referred to as "vinyl chloride-based monomer"). When a vinyl chloride polymer is produced by polymerizing in a solvent, a crosslinking agent is used in an amount of 0.01 to 2 parts by weight per 100 parts by weight of the vinyl chloride monomer, and a reaction conversion rate from the initiation of polymerization to 10% Net stirring power between 0.5 ~ 3kw /
A method for producing a vinyl chloride-based polymer, which is characterized by controlling in the range of m ³ . 2. A diallyl ester and / or triallyl ester of a polyvalent organic acid is used as a crosslinking agent.
Of the vinyl chloride polymer described in 1. 3. The method for producing a vinyl chloride polymer according to claim 1, wherein the vinyl chloride polymer produced has an average degree of polymerization of 500 or more and 1500 or less.