JPH05247106A - Method for suspension polymerization of vinylic monomer - Google Patents

Abstract

PURPOSE:To obtain a method for suspension polymerization in which the polymerization time for one batch can-remarkably be shortened and a high-quality vinylic polymer good in absorptivity of plasticizers and properties of removing monomers with hardly any fish eye can be obtained for various grades. CONSTITUTION:The objective method for suspension polymerization of a vinylic monomer (e.g. vinyl chloride) is to introduce (a) a heated water medium at >=40 deg.C and (b) a dispersion assistant composed of a polyvinyl ester-based polymer having ionic groups at the terminals and <=60mol% saponification degree into a polymerization reactional system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved suspension polymerization method for vinyl monomers. More specifically, the polymerization time for one batch can be greatly shortened, and high productivity and high quality vinyl can be obtained. The present invention relates to a suspension polymerization method capable of obtaining a system polymer.

[0002]

Suspension polymerization of vinyl-based monomers such as vinyl chloride-based monomers is usually carried out in a batch system, and an aqueous medium and a dispersant (suspended) are placed in a polymerization vessel. In general, a turbidity agent), a polymerization initiator, a vinyl chloride-based monomer and the like are charged, and after necessary additives are added, the temperature is raised to carry out the polymerization reaction. But,
In order to improve the productivity, it is required to shorten the time required for one batch of polymerization. For that purpose, it is necessary to shorten the heating time as well as the charging time and the reaction time. is there. Particularly, in a large-sized polymerization vessel or a polymerization vessel with a condenser, the heating capacity of the jacket or the like is relatively small compared to the internal volume, so it was necessary to develop a more effective temperature raising method. For this reason, in suspension polymerization of vinyl chloride-based monomers, a method has been used in which a preheated aqueous medium is charged to eliminate the heating time and improve the productivity.
However, when such a method is used, the obtained vinyl chloride-based resin has a fatal drawback that it has many fish eyes and has poor plasticizer absorbability and demomerization property.

Further, JP-A-56-167745 discloses that the degree of saponification is 65 mol% or more and the average degree of polymerization is 100 to 30.
Polyvinyl alcohol of 00 is used as a dispersant, and saponification degree is 2
Disclosed is an aqueous dispersion containing 0 to 65 mol% and a polyvinyl ester having an average degree of polymerization of 1000 or less as a dispersoid.
In addition, there is a statement that the aqueous dispersion can be used as a dispersion aid for suspension polymerization of vinyl chloride, but no consideration is given from the viewpoint of shortening the polymerization time. others,
In WO91 / 15518, the saponification degree is 60 mol% or less,
It is disclosed that an aqueous dispersion containing a terminal ionic group-modified polyvinyl ester polymer having an average degree of polymerization of 50 to 3000 as a dispersoid is used as a dispersion aid for suspension polymerization of vinyl monomers such as vinyl chloride. ing. According to this technique, vinyl polymer particles having a sharp particle size distribution, a high packing specific gravity and good plasticizer absorbency can be obtained, but no consideration has been made from the viewpoint of shortening the polymerization time and the like. ..

[0004]

[Means for Solving the Problems] Under such circumstances,
The present inventors have conducted extensive studies to overcome the above problems. As a result, when suspension-polymerizing a vinyl-based monomer such as vinyl chloride, a polyvinyl ester-based polymer having an ionic group at a terminal and a saponification degree of 60 mol% or less is added to a polymerization reaction system in a polymerization reaction system. It has been found that all of the above problems can be solved by introducing a dispersion aid consisting of coalescence. The present invention has been completed based on these findings.

That is, in the present invention, in suspension-polymerizing a vinyl-based monomer, (a) a heating aqueous medium at 40 ° C. or higher and (b) a saponification degree having an ionic group at the end of 60 mol%.
The present invention provides a suspension polymerization method for a vinyl-based monomer, which comprises introducing a dispersion aid made of the following polyvinyl ester-based polymer (PVES-based polymer) into a polymerization reaction system.

In the polymerization reaction system of the present invention, (a) the heated water medium and (b) the dispersion aid are introduced into the polymerization reaction system. The heating water medium (a) used here has a temperature of 40 ° C. or higher. The upper limit of this temperature is not particularly limited, and hot water of 95 ° C. or higher may be used. If the temperature of the heated water medium is less than 40 ° C, the polymerization reaction system cannot be sufficiently heated in a short time, and the object of the present invention cannot be achieved. The medium constituting the (a) heated water medium is not limited to pure water, but is used for suspension polymerization of vinyl-based monomers such as an aqueous solution containing various additive components or an aqueous medium containing other organic solvent. A variety of aqueous media can be mentioned as long as they do not interfere. The amount of (a) the heating water medium to be introduced when it is introduced into the polymerization reaction system may be appropriately determined depending on various situations as long as it can sufficiently heat the polymerization reaction system.

Next, the dispersion aid (b) has an ionic group at the terminal and a saponification degree of 60 mol% or less, preferably 10 to
60 mol%, particularly preferably 20-50 mol% PVE
It is composed of an S-based polymer. The polymerization degree of this PVES-based polymer is not particularly limited, but is 50 to 3000.
Is preferable, and 100-2000 is more preferable. In addition,
As the dispersion aid (b), it is particularly effective to use it in the form of an aqueous dispersion containing a self-emulsifying PVES polymer as a dispersoid. As the vinyl ester unit constituting the PVES-based polymer, there are units derived from various vinyl ester compounds. For example, vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, Vinyl caprylate,
Examples thereof include vinyl ester units derived from vinyl versatate, and among these vinyl ester units, vinyl acetate units are industrially preferable.

The degree of polymerization of the above PVES-based polymer is
After substantially completely saponifying an ES polymer and then acetylating it to polyvinyl acetate, the measurement of the intrinsic viscosity in an acetone solution was used to calculate Nakajima's equation (Akio Nakajima: Polymer Chemistry 6 , 4).
51 (1949)). Further, the value of the ratio Pw / Pn of the weight average degree of polymerization (Pw) and the number average degree of polymerization (Pn) is, for example, in the case of a polymer in which vinyl ester units are units derived from vinyl acetate, reacetylation Gel permeation chromatography (GPC) of the obtained polyvinyl acetate polymer
It can be determined by measuring. Also,
Saponification degree means the degree of saponification of vinyl ester component,
When another component is copolymerized, that component is not included.
The degree of saponification can be analyzed by a conventionally known chemical analysis method, nuclear magnetic resonance analysis method, or the like.

There is no particular limitation on the ionic group at the terminal (preferably one terminal) of the PVES polymer of the present invention, but an amino group, an ammonium group, a carboxyl group or a sulfonic acid group may be used. preferable. Examples of the amino group or ammonium group include those derived from thiols represented by the following general formula.

[0010]

[Chemical 1]

And this quaternary compound (a)

[0012]

[Chemical 2]

And this quaternary compound (b)

[0014]

[Chemical 3]

And this quaternary compound (c)

[0016]

[Chemical 4]

In the above general formulas (a) to (d), n is an integer of 0 to 3, m is an integer of 1 to 10, and R ¹ , R ² , R ⁶ , R
⁷ and R ⁸ each represent a hydrogen atom or a methyl group, and R
³ , R ⁴ each represent a lower alkyl group (which may contain a substituent), A is a nitrogen atom of an amine or ammonium and a nitrogen atom of an amide group of the general formula (a) or oxygen of the general formula (c). The group which connects with an atom is shown. Examples of the carboxyl group include those derived from a thiol represented by the following general formula. HS- (CH _{2) p} -COOH and salts thereof (e)

[0018]

[Chemical 5]

In the general formulas (e) and (f), and salt (f), p represents an integer of 0 to 5, and R ⁹ , R ¹⁰ and R ¹¹ are each a hydrogen atom or a lower alkyl group (having a substituent May be included). Examples of the sulfonic acid group include those derived from a thiol represented by the following general formula.

[0020]

[Chemical 6]

[0021]

[Chemical 7]

[0022]

[Chemical 8]

[0023]

[Chemical 9]

In the general formulas (g) to (j), r is 1 to
Indicates an integer of 4, R¹²~ R²⁰Is a methyl group or
Represents a hydrogen atom, M is a hydrogen atom, an alkali metal or
Indicates an ammonium ion. When r is plural, r
There are as many Rs as there are¹⁵, R ¹⁶, R¹⁸, R¹⁹Are the same
But it can be different.

The terminal ionic group of the PVES polymer of the present invention is preferably an ionic group such as an amino group, an ammonium group, a carboxyl group or a sulfonic acid group as exemplified above, and a carboxyl group is preferable. More preferable. These ionic groups include salts thereof,
From the viewpoint of water dispersibility or water solubility of the ES polymer, an alkali metal salt is more preferable. The above-mentioned PVES-based polymer having an ionic group is not particularly limited in its production method, and various methods can be adopted,
For example, (i) a compound having a functional group such as an alcohol, an aldehyde, or a thiol having an ionic group is allowed to coexist as a chain transfer agent to polymerize a vinyl ester, and then saponified to produce a PV having an ionic group at a terminal.
Examples thereof include a method of obtaining an ES polymer, and (ii) a method of introducing an ionic group into a terminal of a PVES polymer by a chemical reaction. However, as a method of introducing an ionic group at the terminal more economically and efficiently and obtaining an excellent dispersion aid for suspension polymerization, a chain transfer agent having an ionic group,
Particularly preferred is a method in which vinyl esters such as vinyl acetate are polymerized in the presence of a thiol having these functional groups, and then saponified (see JP-A-57-28121 and 57-105410).

In the presence of a thiol having an ionic group,
When polymerizing vinyl esters such as vinyl acetate, the amount and method of addition of thiol to the polymerization system may be appropriately selected. Thiol acts as a chain transfer agent, and the amount and method of addition of thiol to the polymerization system affect the degree of polymerization and the distribution of the degree of polymerization of the resulting polymer. It is decided appropriately from the aspect.
However, in order to efficiently introduce an ionic group at the end of the PVES polymer, particularly at one end, and obtain an excellent dispersion aid, a thiol is added according to the reaction rate of the vinyl ester in the polymerization system. It is preferable that the amount of thiol in the reaction system does not change much with respect to the vinyl ester. By doing so, the introduction efficiency of the ionic group at the terminal is improved, the distribution of the degree of polymerization is narrowed, and a dispersion aid having excellent performance is obtained, which is preferable. In particular, the ratio P of the weight average degree of polymerization (Pw) and the number average degree of polymerization (Pn), which indicates the degree of the degree of polymerization distribution,
It is desirable that w / Pn does not exceed 4.0.

PVE having an ionic group at the end of the present invention
As described above, it is essential for the S-based polymer to have an ionic group at the terminal, but as long as the effect as a dispersion aid is not impaired, the side chain has the same or different ion as the terminal group. It may have a sexual group. It is also possible to introduce a nonionic group into the side chain. The type of polymerization of the polyvinyl ester, which is the raw material of the PVES polymer of the present invention, is
Any conventionally known method such as bulk polymerization, solution polymerization, suspension polymerization, dispersion polymerization or emulsion polymerization can be adopted, but industrially solution polymerization using methanol, toluene or the like is most preferable. Further, the polymerization operation can be carried out by any of batch process, semi-batch process and continuous process.

As the initiator used in the polymerization for obtaining the dispersion aid of the present invention, a known radical polymerization initiator is usually used. Examples include 2,2'-azobisisobutyronitrile;2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile); benzoyl peroxide; diisopropyl peroxydicarbonate; potassium persulfate and the like. Be done. The polymerization temperature can be appropriately set depending on the initiator used, but is preferably 10 to 90 ° C. The method for obtaining a PVES polymer having an ionic group at the terminal and having a saponification degree of 60 mol% or less according to the present invention is a generally known method, that is, an unsaponifiable PES having an ionic group at the terminal.
The method of saponifying a VES polymer is mentioned. As the saponification method, either alkali saponification or acid saponification can be adopted, but industrially, a methanol solvent is used for NaOH.
The methanol decomposition with CH ₃ ONa as a catalyst is most advantageous. The saponification temperature is not particularly limited, but it is preferably carried out at 20 to 60 ° C. from the viewpoint of preventing coloration of the obtained PVES polymer having a saponification degree of 60 mol% or less. Further, the amount of NaOH or CH ₃ ONa used as a catalyst is usually 0.2 mol or less per 1 mol of the vinyl ester unit, which prevents coloring of the obtained PVES polymer and keeps the amount of sodium acetate low. Is preferred. When the functional group introduced at the terminal includes one that consumes an alkali such as an acid, it is desirable to carry out saponification by adding an amount of the alkali more than the above range.

Various methods can be considered for using the dispersion aid of the present invention. For example, a method of charging the dispersion aid as a powder into a polymerization tank (method I), an organic solvent such as methanol for the dispersion aid, and the like. A method of charging a solution as a solution in a polymerization tank (method II), an aqueous dispersion of a dispersion aid is mixed with an aqueous solution of a main dispersant which is optionally used together, and the resulting mixed solution is charged into a polymerization tank. Method (Method III), a method of separately charging an aqueous dispersion of a dispersion aid and an aqueous solution of a main dispersant to be used in combination into a polymerization tank (Method IV), and the like. Of these methods, Method I is often industrially unsuitable, and Method II involves the problem of environmental pollution due to an aqueous medium after suspension polymerization due to the incorporation of an organic solvent in the aqueous medium. Cheap. On the other hand, Method III or Method IV is preferable from the industrial and environmental viewpoints. Among these Method III and Method IV, Method IV is most preferable in view of the processing characteristics of the resulting vinyl resin.

The PVES polymer as the dispersion aid (b) of the present invention can be used in combination with other main dispersants such as polyvinyl alcohol (PVA). When the (b) dispersion aid of the present invention is used in combination with the main dispersant, the content of the dispersion aid is not particularly limited, but is preferably 10 to 70% by weight, more preferably 10 to 50% by weight. The ratio of the dispersion aid and the main dispersant (dispersion aid / main dispersant) is 1
If it is smaller than 0/90, the effect of addition is small,
If this ratio is greater than 70/30, the polymerization stability may be adversely affected. The main dispersant used in combination with (b) the dispersion aid of the present invention is not particularly limited as long as it is used as a dispersant for suspension polymerization of a vinyl compound, and above all, the degree of polymerization is 300 to 3000 and Saponification degree 6
0 to 90 mol% of PVA or PVA-based polymer is particularly preferable, and these may have an ionic group or a nonionic group in the side chain. Further, a PVA or PVA-based polymer having a saponification degree of less than 60 mol% can be used in combination with the dispersant comprising the above-mentioned dispersion aid and main dispersant. In addition, conventionally known cellulose derivatives can also be used as the main dispersant.

As mentioned above, the suspension polymerization method of the present invention comprises:
A heating water medium of 40 ° C. or higher is used at the time of introduction into the polymerization reaction system, that is, at the time of charging, and the charging order and ratio of vinyl monomer, polymerization initiator, main dispersant, heating water medium and other additives Is not limited in any way.

As various additives used as necessary in the present invention, acetaldehyde, butyraldehyde, trichlorethylene, perchlorethylene, mercaptans and other polymerization degree regulators, phenol compounds, sulfur compounds, N-oxide compounds, etc. Polymerization inhibitors, etc. Further, it is optional to add a pH adjuster, a scale inhibitor, a cross-linking agent, etc., and a plurality of the above additives may be used in combination. It is also effective to attach a condenser such as a condenser to the polymerization device. On the other hand, the polymerization initiator may also be one that has been conventionally used for the polymerization of vinyl-based monomers such as vinyl chloride, which includes diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxyethyl. Percarbonate compounds such as peroxydicarbonate, perester compounds such as t-butylperoxyneodecanate, α-cumylperoxyneodecanate, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2- Examples thereof include peroxides such as peroxyphenoxyacetate and azo compounds such as azobis-2,4-dimethylvaleronitrile and azobis (4-methoxy-2,4-dimethylvaleronitrile). Further, these may be used in combination with potassium persulfate, ammonium persulfate, hydrogen peroxide and the like. This addition amount is 0.02 to 0.1 per 100 parts by weight of the vinyl-based monomer.
A range of 3 parts by weight is preferred.

The dispersion aid of the present invention is added as a powder, as a methanol solution, or as an aqueous dispersion to a heating aqueous medium of a suspension polymerization system. It is preferably added to a heated aqueous medium. The vinyl-based monomer to be polymerized by the method of the present invention includes vinyl chloride alone and a monomer mixture mainly composed of vinyl chloride (vinyl chloride 50% by polymerization or more),
Examples of the comonomer copolymerized with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate,
Acrylic or methacrylic acid esters such as methyl acrylate and ethyl acrylate, olefins such as ethylene and propylene, maleic anhydride, acrylonitrile, itaconic acid, styrene, vinylidene chloride, vinyl ether, and other vinyl chloride copolymerizable monomers Is exemplified. Furthermore, the method of the present invention can also be applied to homopolymerization or copolymerization of the above vinyl compound containing no vinyl chloride.

In carrying out the method of the present invention, the charging ratio of each component, the polymerization temperature, etc. are determined in accordance with the conditions conventionally used in the suspension polymerization of vinyl monomers such as vinyl chloride. It is sufficient, and it should not be particularly limited.

[0035]

The present invention will be described in more detail with reference to the following examples, but the method of the present invention is not limited to these examples. In the following examples, "part" means "part by weight". Examples 1 to 28 and Comparative Examples 1 to 4 Suspension polymerization of vinyl chloride was carried out by the following method using the main dispersant and dispersion aid shown in Table 1. That is, the main dispersant (PV
A) A 2% by weight aqueous solution, a predetermined amount of a dispersion aid (polyvinyl acetate; PVAc) 2% by weight aqueous solution, and 50% by weight toluene solution of diisopropyl peroxydicarbonate (0.009 parts) were charged into the autoclave. 50
Degassed to mmHg to remove oxygen, then deionized water 4 heated with 30 parts of vinyl chloride monomer and 63 ° C
5 parts were charged and the polymerization was carried out with stirring. The internal temperature after charging was 57 ° C. At the start of the polymerization, the pressure in the autoclave was 8.5 kg / cm ² G, but it reached 4.5 kg / cm ² G 7 hours after the start of the polymerization, so the polymerization was stopped at this point and the unreacted vinyl chloride was removed. The monomer was purged, the contents were taken out and dehydrated and dried. The vinyl chloride resin obtained had a polymerization yield of 88% and an average degree of polymerization of 1050.
The performance of this vinyl chloride resin is shown in Table 2.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

[Table 5]

[0041]

[Table 6]

[0042]

[Table 7]

[0043]

[Table 8]

(1) Particle size distribution The particle size distribution was measured by dry sieve analysis using a wire mesh based on Tyler mesh. (2) Fisheye measurement method 100 parts by weight of vinyl chloride resin obtained by polymerization, 1 part by weight of tribasic lead sulfate, 1.5 parts by weight of lead stearate, 0.2 parts by weight of titanium dioxide, 0.1 parts of carbon black. 25 g of a composition obtained by mixing 50 parts by weight of dioctyl phthalate
Was kneaded with a roll at 145 ° C. for 5 minutes and separated as a 0.2 mm thick sheet, and the number of transparent particles in 100 cm ² of this sheet was shown. (3) Absorption of plasticizer In a planetary mixer connected to a plastograph,
Add 400 g of vinyl chloride resin powder obtained by polymerization, preheat (4 minutes) while stirring at 60 rpm, and heat at 80 ° C.
After that, 200 g of dioctyl phthalate was added thereto, and the time was defined as the plasticizer absorbability (minutes) until the time when the torque decreased due to the addition. (4) Residual vinyl chloride monomer The vinyl chloride monomer content in the vinyl chloride resin was quantified by headspace gas chromatography.

[0045]

As described above, according to the present invention, the polymerization time for one batch can be greatly shortened, and moreover, various types of grades have little fish eyes, good plasticizer absorbability and good demonomer property. A high quality vinyl polymer can be obtained.

Claims (2)

[Claims] 1. A suspension of a vinyl-based monomer, wherein (a) a heated aqueous medium at 40 ° C. or higher and (b) an ionic group at the terminal and a polyvinyl ester-based polymer having a saponification degree of 60 mol% or less. A suspension polymerization method of a vinyl-based monomer, which comprises introducing a dispersion aid consisting of 2. The suspension polymerization method according to claim 1, wherein the dispersion aid is an aqueous dispersion containing a polyvinyl ester polymer having a self-emulsifying property as a dispersoid.