JPH07278207A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To produce a vinyl chloride polymer having a high rate of meeting in gelation, a high bulk specific gravity and an excellent moldability by polymerizing a vinyl chloride monomer in the presence of a specified polymerization initiator under specified conditions. CONSTITUTION:A vinyl chloride monomer component comprising a vinyl chloride monomer itself or a mixture of a major proportion of a vinyl chloride monomer with a monomer copolymerizable therewith is polymerized in an aqueous medium in the presence of two polymerization initiators satisfying the relationships: 20 deg.C<=T1<T2<=80 deg.C, 30 deg.C<=t1<=50 deg.C, 45 deg.C<=t2<=60 deg.C, t1<t2, and 0.5<=(t2-t2)/(T2-T1)<=3, [wherein t1 and t2 are the 10-hr half-life temperatures ( deg.C) of the polymerization initiators used, T1 is the initial polymerization temperature ( deg.C), and T2 is the final polymerization temperature ( deg.C)] and used in amounts to give a weight ratio of 20/80 to 80/20 under the conditions in which the polymerization temperature is raised with the lapse of time during the period of time corresponding to at least 50% of the entire period in which the polymerization reaction proceeds, and the width of the temperature rise is within a range of 10-35 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a vinyl chloride polymer. More particularly, the present invention relates to a method for stably producing a vinyl chloride polymer having improved moldability, particularly having a large bulk specific gravity and a high gelation melting rate during processing.

[0002]

2. Description of the Related Art Vinyl chloride polymers are usually vinyl chloride monomers or a mixture of copolymerizable monomers mainly composed of vinyl chloride monomers (hereinafter, these are collectively referred to as "vinyl chloride"). System monomer ", and the polymer obtained by polymerizing these is referred to as" vinyl chloride polymer ".) In the presence of a polymerization initiator in an aqueous medium containing an emulsifier or a dispersant. It is produced by suspension polymerization.

Generally, the moldability of vinyl chloride resin made of vinyl chloride polymer depends strongly on the particle morphology,
Increasing the bulk specific gravity, the internal void volume, and the gelling melting rate of the vinyl chloride resin are important factors for improving moldability. The present inventors have previously used a method for producing a vinyl chloride-based polymer by polymerizing a vinyl chloride-based monomer in an aqueous medium as a method for increasing the bulk specific gravity and gelation melting rate of the vinyl chloride-based resin. , A method of performing polymerization while raising the polymerization temperature for 50% or more of the entire period of the progress of the polymerization reaction (Japanese Patent Laid-Open No. 61-1261).
No. 12) was proposed.

However, in the above-mentioned method, the larger the increase change width of the polymerization temperature in the polymerization reaction (hereinafter referred to as "temperature rising width"), the larger the bulk specific gravity and gelation melting rate, but If it is too large, the heat generation becomes too large at the end of the polymerization reaction and cooling becomes difficult, or the polymerization reaction is not completed at the end of the reaction due to lack of polymerization initiator, and the polymerization reaction does not complete within the desired time. There was such a problem.

[0005]

[Problems to be Solved by the Invention] Polymerization is sufficiently performed even in the final stage of the polymerization reaction, and a vinyl chloride polymer having a large bulk specific gravity and a high gelation melting rate of the obtained vinyl chloride polymer resin is obtained. It is an object of the present invention to provide a manufacturing method.

[0006]

The summary of the present invention is as follows.
In the method for producing a vinyl chloride polymer by polymerizing a vinyl chloride monomer or a mixture of copolymerizable monomers mainly composed of a vinyl chloride monomer in an aqueous medium, the period during which the polymerization reaction proceeds The polymerization reaction is carried out while the polymerization temperature is increased with time in the period of 50% or more of the whole, and the change range of the increase is in the range of 10 to 35 ° C. Of a vinyl chloride-based polymer, characterized in that it is carried out in the presence of two kinds of polymerization initiators satisfying the above conditions, and the weight ratio of the two kinds of polymerization initiators is 20/80 to 80/20. Manufacturing method.

[0007]

## EQU2 ## 20 ° C. ≦ T ₁ <T ₂ ≦ 80 ° C. (1) 30 ° C. ≦ t ₁ ≦ 50 ° C. (2) 45 ° C. ≦ t ₂ ≦ 60 ° C. (3) t ₁ <t ₂ (4) However, t ₁ , t ₂ : 10-hour half-life temperature (° C.) T ₁ : polymerization initiation temperature (° C.) T ₂ : polymerization termination temperature (° C.) of the weight initiator used, the present invention will be described in more detail below. .

The vinyl chloride-based monomer used in the method of the present invention includes not only the vinyl chloride monomer itself but also a mixture of copolymerizable monomers mainly composed of the vinyl chloride monomer. . Examples of the monomer copolymerizable with the vinyl chloride monomer include olefins such as ethylene and propylene, vinyl acetates such as vinyl acetate and vinyl stearate, vinyl ethers such as ethyl vinyl ether and cetyl vinyl ether, and acrylic acid esters. , Unsaturated carboxylic acid derivatives such as maleic acid or fumaric acid esters and anhydrides, and unsaturated nitriles such as acrylonitrile. The copolymerizable monomer is usually used in a proportion of 20% by weight or less based on the vinyl chloride monomer.

For the polymerization of the vinyl chloride-based monomer in the method of the present invention, a generally known polymerization recipe of the vinyl chloride-based monomer in an aqueous medium is widely adopted. The dispersant and the emulsifier to be used do not have to be special ones, and widely used dispersants and emulsifiers can be used. For example, as the dispersant or emulsifier, a partially saponified product of polyvinyl acetate, an acrylic acid copolymer, a maleic anhydride copolymer, a cellulose derivative, gelatin, a protective colloidal drug such as starch, or a natural polymer compound is used. , Esters of higher fatty acids and polyhydric alcohols, nonionic surfactants such as polyoxyethylene derivatives, metal salts of higher fatty acids, and anionic surfactants such as alkali salts of higher alcohol sulfate esters are used. The amount of these dispersants and emulsifiers used is not particularly limited, and its type, stirring efficiency, polymerization temperature, type and composition of other monomers copolymerizable with vinyl chloride monomer, vinyl chloride polymer The amount is generally 0.01 to 2.0% by weight, preferably 0.03 to 1% by weight, based on the total amount of the vinyl chloride-based monomer, although it may vary depending on the particle size and the like.

As the polymerization initiator used in the present invention, t-butylperoxypivalate (10-hour half-life temperature (hereinafter the same): 55 ° C.), t-hexylperoxypivalate (53.2 ° C.) , T-butyl peroxy neodecanoate (46.5 ° C.), cumyl peroxy neodecanoate (36.6 ° C.), bis (2-ethylhexyl) peroxydicarbonate (43.5 ° C.),
Diisopropyl peroxydicarbonate (40.5
° C, but with an initial concentration of 0.05 mol / l) or other organic peroxide, azobis (dimethylvaleronitrile) (51 ° C,
However, azo compounds such as (in toluene solvent) and the like,
From such a polymerization initiator, depending on the polymerization start temperature and the polymerization end temperature, 2 which satisfies the above formulas (2) to (5)
A type of polymerization initiator is selected and used.

The 10-minute half-life temperature of the above-mentioned polymerization initiator is defined as the decomposition temperature at which the concentration of the polymerization initiator having an initial concentration of 0.1 mol / l becomes 1/2 in 10 hours in a benzene solvent. T ₁ and T ₂ used in the method of the present invention are selected according to the average degree of polymerization of the intended vinyl chloride polymer, and the polymerization initiator used at that time is 10
The time half-life temperature is selected from those satisfying the formulas (2) to (5) as described above, and particularly the following formulas (6) and (7)

[0012]

Equation 3] is preferably selected from among the _{T 1 -15 ≦ t 1 ≦ T} 1 -5 (6) T 2 -20 ≦ t 2 ≦ T 2 -10 (7) fulfills this time,
It becomes easy to maintain both good reaction activity and good reaction controllability.

The combination of the polymerization initiators used in the method of the present invention can have a difference in 10-hour half-life temperature of 15 ° C. or more, and has an average polymerization degree range (for example, 800 to 800) which is often used in vinyl chloride resins. 1300 etc.) is suitable for the polymerization temperature range that covers the above.
Examples of such a combination of polymerization initiators include t-
Hexyl peroxypivalate (hereinafter referred to as "HPV") and cumyl peroxy neodecanoate (hereinafter referred to as "C
ND ”).

Under the conditions of the above equations (1) and (4), (2),
When a polymerization initiator not satisfying the formulas (3) and (5) is used, for example, when a polymerization initiator having t ₁ <30 ° C. is used, the decomposition rate of the polymerization initiator at the initial stage of the polymerization reaction is high. , The reaction controllability deteriorates. Further, when 60 ° C. <t ₂ , the decomposition rate of the polymerization initiator is slow and the reaction is thermally stable due to a rapid reaction at the end of the reaction or the polymerization initiator remaining in the obtained vinyl chloride polymer. It is easy to cause deterioration of sex.

[0015]

[Equation 4] In such a case, the reaction rate may be significantly reduced at the final stage of the polymerization reaction, or the reaction may be difficult to occur at the initial stage, resulting in a runaway reaction accompanied by rapid heat generation at the final stage.

[0016]

[Equation 5] In this case, there is a difference between the polymerization temperature and the decomposition of the polymerization initiator, the reaction rate tends to be insufficient, and the reaction controllability tends to deteriorate.

The total amount of these polymerization initiators used is generally in the range of 0.01 to 1.0% by weight, based on the total amount of vinyl chloride-based monomers. The weight ratio of the initiator is [t ₁ ] / [t ₂ ] = 20/8
It is set to 0 to 80/20 (however, [t ₁ ] and [t ₂ ] mean the compounding amounts of the polymerization initiators having 10-hour half-life temperatures t ₁ and t ₂ , respectively).

When [t ₁ ] / [t ₂ ] is smaller than 20/80, the exothermic amount is small in the initial stage of the reaction, and the exothermic amount is large in the final stage, and there is a possibility that the temperature inside the polymerization reactor cannot be controlled.
On the other hand, if it is larger than 80/20, heat is generated from the early stage of the reaction, but the heat generation becomes weak at the final stage of the reaction, and the reaction may be slowed or stopped. In the polymerization reaction of the present invention, generally known polymerization aids, for example, trichlorethylene, dodecyl mercaptan, 2-mercaptoethanol, chain transfer agents such as propionaldehyde,
An antioxidant or the like can be optionally used.

In carrying out the method of the present invention, the vinyl chloride-based monomer may be charged all at once before the initiation of polymerization,
Alternatively, a part of the vinyl chloride-based monomer may be charged before the start of the polymerization, and the rest may be charged continuously or after the start of the polymerization. By the way, in the method of the present invention, the polymerization reaction of the vinyl chloride-based monomer is carried out while raising the polymerization temperature with time in a period of 50% or more of the entire period of the progress of the polymerization reaction.

The above-mentioned "entire period during which the polymerization reaction proceeds" means that the vinyl chloride-based monomer is polymerized in the presence of a polymerization initiator and other additives according to a usual vinyl chloride-based monomer polymerization recipe. In this case, the period from the time when the polymerization initiator starts to decompose due to the temperature rise of the polymerization reaction system and the polymerization of the vinyl chloride-based monomer starts to the time when the target polymerization rate is reached and the polymerization reaction ends. Means the whole.

Therefore, conventionally, after charging the raw materials into the polymerization reactor, until the polymerization reaction starts, that is, until the polymerization initiator starts to decompose and the exothermic reaction starts, for example, the polymerization reactor. Heat by a normal heating method such as circulating hot water in the jacket attached to, and raise the temperature rapidly,
Then, during the period from the start of the polymerization reaction to the end of the polymerization reaction, that is, during the progress of the polymerization reaction, a large increase in temperature due to heat generation is controlled by a method such as circulating cooling water in the jacket. While the polymer having a predetermined degree of polymerization was obtained by maintaining the temperature at a constant temperature, in the method of the present invention, the polymerization temperature was changed with time for 50% or more of the entire period in which the polymerization reaction proceeded. The polymerization reaction is carried out while controlling the degree of cooling so as to increase at an appropriate rate.

The rapid temperature rise in "less than 50% of the entire period during which the polymerization reaction proceeds" is caused by the remaining polymerization initiator having a 10-hour half-life temperature of t ₁ (hereinafter referred to as "low-temperature active polymerization initiator"). The reaction temperature becomes uncontrollable due to the rapid decomposition of the reaction mixture, or the reaction exotherm becomes non-uniform because most of the low-temperature active polymerization initiators have to be heated up after decomposition, and thus the reaction control It is difficult and requires a large heat removal capacity of the polymerization reactor, resulting in low productivity.

Next, comparing the conventional method of carrying out the polymerization reaction by keeping the polymerization reaction system at a constant temperature (hereinafter, referred to as "constant temperature reaction method") and the method of the present invention, the former is the same as the polymerization temperature. The latter is limited only by its “height”, whereas the latter is controlled by both its “height” and “temperature rise width”. However, the setting of the "height" and the "temperature rise range" of the polymerization temperature in the method of the present invention is essentially determined experimentally so that the intended vinyl chloride polymer can be obtained. Specifically, it can be decided according to certain guidelines.

That is, first, it is known that the degree of polymerization of the vinyl chloride polymer produced in the constant temperature reaction method is governed by the "highness" of the polymerization temperature, which is also essential in the method of the present invention. Is similar to. Therefore, for example, considering the "average height" of the polymerization temperature based on the change range of the polymerization temperature in the method of the present invention, the "average height" is defined as the product of the desired degree of polymerization in the constant temperature reaction method. By setting the polymerization temperature in the vicinity of the "high" of the polymerization temperature for obtaining the product, a product having a substantially desired polymerization degree can be obtained. Of course, the “constant temperature reaction method” and the so-called “temperature rising reaction method” of the present invention are not the same, and the latter is also affected by the temperature rising pattern.
That is, the average degree of polymerization of all the obtained polymers is the weighted average of the degree of polymerization of the polymer formed at each point of the temperature raising process, and the amount of the polymer produced at that time, and the amount produced. It is also affected by the selection of the heating pattern.
Therefore, it is desirable to set the accurate "average height" experimentally after determining the temperature rise pattern.

Next, the "temperature rise range" of the polymerization temperature mainly controls the effect of continuous temperature rise in the method of the present invention.
In the present invention, the "temperature rise width" is in the range of 10 to 35 ° C, preferably 15 to 30 ° C. "Change range" is 10
If it is lower than 0 ° C, the improvement effect by the production method of the present invention is not sufficient, and it is possible to obtain a vinyl chloride-based polymer having a large bulk specific gravity and a high gelation melting rate as compared with the vinyl chloride-based polymer obtained by the conventional method. It will be difficult. On the other hand, if the temperature is higher than 35 ° C., the exothermic heat may be too large at the end of the polymerization reaction and cooling may be difficult.

"Average height" and "temperature rise range" of polymerization temperature
Since a suitable value of is also affected by the performance of the specific reaction system, mainly the monomer composition and the polymerization initiator, it is desirable to empirically select the specific reaction system including these. The specific range of change in the polymerization temperature, that is, the temperature increase start temperature and the temperature increase end temperature in the polymerization temperature range can be determined, for example, as follows.

That is, as a model, over the entire temperature rise range,
Considering the case where the polymerization reaction rate is constant and the entire period of the polymerization reaction is the temperature rising period, the polymerization temperature required to obtain a vinyl chloride polymer having a desired degree of polymerization in the constant temperature reaction method is t _0. (° C), the temperature rise width in the temperature rising reaction method is
Assuming t (° C.), the temperature rise start temperature is (t ₀ −Δt),
The temperature rise end temperature is (t ₀ + Δt), and therefore the polymerization temperature range is

[0028]

(6) (t ₀ −Δt) to (t ₀ + Δt).

The above description is based on the most general linear temperature rising pattern, and in this case, almost the expected result can be obtained. Since the reaction results of the "warm reaction method" are also affected by the temperature rise pattern, some modifications should be made experimentally according to the desired product, especially when a non-linear temperature rise pattern is adopted. Is desirable.

The heating rate of the polymerization temperature in the method of the present invention may be a heating rate uniquely obtained from the rising temperature width of the polymerization temperature and the heating period (that is, a linear heating pattern). It is the simplest and gives good results. For example, when the polymerization temperature range is 50 to 60 ° C., the total polymerization reaction time is 8 hours, and the heating period is 5 hours, the heating rate may be 2 ° C./hr. It is generally preferable to change the heating rate during heating, that is, to provide a bending point in the heating pattern, because an excessive heating or cooling capacity at that point is required. However, fluctuations that are allowable in temperature control do not significantly affect the result, and are therefore acceptable as one embodiment of the present invention. For example, the method of changing the temperature raising rate from 1.5 ° C./hr to 0.5 ° C./hr during the reaction, or providing a period for maintaining a constant temperature before and after that is also a method of increasing the temperature raising period. It is acceptable as one embodiment of the present invention if the total is set to 50% or more of the total polymerization reaction period. In the method of the present invention, the rate of temperature increase of the polymerization temperature is preferably 10 ° C./hr or less from the viewpoint of reaction controllability.

The control of the polymerization reaction in the method of the present invention is not particularly limited as long as it is a control method that enables a smooth temperature rise, but for example, feedback control incorporating a computer, feedforward control, etc. It is suitable in terms of productivity, controllability, and stability. The method of the present invention can be applied to any method as long as it is a polymerization of a vinyl chloride-based monomer in an aqueous medium, but it is particularly applicable to a suspension polymerization method using an oil-soluble polymerization initiator. , Industrially most useful and high value.

[0032]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. The physical properties of the obtained vinyl chloride polymer were evaluated by the following physical property measuring methods.

Physical property measurement method Average degree of polymerization and bulk specific gravity: Determined according to the method described in JIS K-6721. Gelation time Sample 60 blended with 100 parts by weight of PVC, 3 parts by weight of lead-based powder stabilizer and 0.5 parts by weight of barium-based powder stabilizer
g to Brabender Plasticorder (187 ° C, 4
The mixture was kneaded at 5 rpm) and the time until the maximum torque was exhibited was measured.

Examples 1 and 2 100 kg of vinyl chloride monomer, 150 kg of deionized water, partially saponified polyvinyl acetate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) were placed in a stainless steel polymerization vessel equipped with a stirrer and a jacket having an internal volume of 400 liters. , Gohsenol KH-17, average polymerization degree 2300, saponification degree 88.5%) 60 g, and the polymerization initiator shown in Table 1 were charged. After the completion of charging, warm water was circulated in the jacket and heated rapidly to the temperature rising start temperature shown in Table 1 to start the polymerization reaction. Then, the temperature was continuously raised, the temperature was finished at the temperature shown in Table 1, and thereafter this temperature was maintained until the desired reaction conversion rate (80%) was reached. The results of physical property evaluation of the thus obtained vinyl chloride polymer (hereinafter referred to as “PVC”) are shown in Table 2.

Comparative Examples 1 to 10 Preparation was carried out in the same manner as in Example 1 except that the polymerization initiator and the amount used were changed as shown in Table 1. Then, the temperature rising end temperature was maintained until the desired reaction conversion rate (80%) was reached in the same manner as in Example 1 except that the polymerization reaction was performed under the reaction conditions shown in Table 1. The results of evaluation of the physical properties of the PVC thus obtained are shown in Table-2.

In Comparative Examples 1 to 3, since the temperature rise width is small, PV having a small gelling and melting rate and a low bulk specific gravity as compared with the Examples.
C was obtained. In Comparative Example 4, the reaction rate decreased remarkably at the end of the reaction, the desired reaction rate could not be achieved, and the reaction was stopped halfway. In Comparative Examples 5 to 7, although there was almost no heat generation in the early stage of the reaction, a rapid heat generation occurred in the final stage of the reaction, and it became extremely difficult to control the reaction. Comparative Example 8
In the case of -10, although the heat generation was considerably close to the limit cooling capacity from the early stage to the middle stage of the reaction, the heat generation stopped at the final stage of the reaction and the target reaction conversion rate (80%) was not reached.

Comparative Example 11 Charge was carried out in the same manner as in Example 1 except that the polymerization initiator and the amount thereof used were changed as shown in Table 1. Then, the polymerization reaction is carried out under the reaction conditions shown in Table-1,
The reaction temperature was changed from 48 ° C to 68 ° C at a reaction conversion rate of 60%.
Although the temperature was raised for 0 minutes, the remaining cumyl peroxyneodecanoate (CND) was rapidly decomposed, the heat generation was increased, and the reaction control became extremely difficult.

Comparative Example 12 Charge and polymerization reaction were carried out in the same manner as in Comparative Example 11 except that the amount of the polymerization initiator used was changed as shown in Table 1. Since the reaction rate decreased because the amount of CND was insufficient before the reaction conversion rate reached 60%, the temperature was raised from 48 ° C to 68 ° C over 30 minutes. As a result, the reaction rate increased remarkably, the cooling load became extremely large, and the reaction control was extremely difficult.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

EFFECTS OF THE INVENTION According to the present invention, a PVC having a remarkably high gelling and melting rate, a large bulk specific gravity and an excellent moldability as compared with the PVC obtained by the conventional method.
Can be manufactured stably.

Claims (2)

[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"). In the method of producing a vinyl chloride polymer by performing a polymerization reaction in a room temperature, the polymerization reaction is performed while the polymerization temperature is increased with time in a period of 50% or more of the entire period in which the polymerization reaction proceeds, Is 10 to 3
Within the range of 5 ° C., the polymerization reaction is performed by the following formulas (1) to (5)
To be carried out in the presence of two kinds of polymerization initiators satisfying the above conditions, and the weight ratio of the two kinds of polymerization initiators is 20/8.
The method for producing a vinyl chloride polymer is characterized in that it is 0 to 80/20. ## EQU1 ## 20 ° C. ≦ T ₁ <T ₂ ≦ 80 ° C. (1) 30 ° C. ≦ t ₁ ≦ 50 ° C. (2) 45 ° C. ≦ t ₂ ≦ 60 ° C. (3) t ₁ <t ₂ (4) However, t ₁ and t ₂ : 10-hour half-life temperature (° C) of the weight initiator used T ₁ : Polymerization start temperature (° C) T ₂ : Polymerization end temperature (° C) 2. The method for producing a vinyl chloride polymer according to claim 1, wherein the two types of polymerization initiators are t-hexylperoxypivalate and cumylperoxyneodecanoate.