JPS6172008A - Emulsion polymerization of acrylic monomer - Google Patents

Abstract

PURPOSE:Monomers containing (meth) acrylic acid esters is used as a major component to effect polymerization using a sulfonated soap as an emulsifier in the presence of an alkali metal hydroxide in such an amount as ion quantity and pH can be specified, thus giving the title polymer with high resistance to whitening with hot water. CONSTITUTION:When monomers mainly consisting of an acrylic ester and/or methacrylic ester such as methyl methacrlate are polymerized in an aqueous medium using an emulsifier mainly consisting of sulfonate soap, at least one of ions such as hydroxide, carbonate or bicarbonate ions from alkaline earth metal hydroxide, carbonate or bicarbonate is added to the aqueous medium for polymerization system so that its amount becomes 0.0001-0.01 g.ion/liter and the pH in the polymerization system is in a range from 5.0-9.0 to effect emulsion polymerization.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to a method of emulsion polymerization, and more specifically, to emulsifying a monomer containing (meth)acrylic ester using anionic Sumikata Ken. It relates to a method of polymerization. [However, (meth)acrylic acid hereinafter refers to both or either of acrylic acid and methacrylic acid;
Acrylate refers to acrylate and/or methacrylate. 〕 ``Prior art'' Conventionally, emulsion polymers of monomers containing (meth)acrylic acid esters have been used as molding materials for films, etc., but undecomposed polymerization initiators remain and heat Stability is not good. Japanese Patent Publication No. 59-27762 discloses a method for smoothly carrying out this emulsion polymerization. That is, when the pH of the polymerization system is adjusted to 5.5 to 9.5 using borate ions, polymerization can be maintained stably when fatty acid soaps are used as emulsifiers.

In fact, when this method is applied to emulsifiers such as alkyl sulfate ester salts and noalkyl sulfosuccinates, undecomposed substances of the polymerization initiator after the completion of the polymerization reaction are reduced, and the thermal stability of the polymerization reaction product is also improved. However, when this polymerization reaction product is used as a molded product such as a sheet film, if the molded product is immersed in hot water, a trace amount of boric acid will be incorporated into the molded product, causing a whitening phenomenon. This is a major drawback.

"Problems to be Solved by the Invention" In view of the above circumstances, the inventors of the present invention have conducted various studies and found that alkali metal hydroxides, alkaline earth metal hydroxides, metal salts of carbonates, or heavy By using a metal carbonate, it is possible to stabilize the polymerization system, reduce undecomposed substances of the polymerization initiator after the polymerization reaction is completed, and improve the thermal stability of the polymerization reaction product. Moreover, it has been found that when the polymerization reaction product is made into a film, a resin having excellent hot water whitening resistance can be obtained.

``Means for Solving the Problems'' That is, the present invention consists of a monomer containing an acrylic ester and/or a methacrylic ester as a main component, and an emulsifier containing a sulfonic acid soap as a main component, in an aqueous medium. During polymerization, one or more ions selected from aqueous ions, carbonate ions, and bicarbonate ions are present in the aqueous dispersion medium constituting the polymerization system at 0.0001 to 0.01 g ion/l. and the pH of the polymerization system is 5.
．． This is an emulsion polymerization method characterized by the presence of an alkali metal hydroxide, an alkaline earth metal hydroxide, a metal salt of carbonate, or a metal bicarbonate so that the hydroxide concentration is in the range of 0 to 9.0.

The present invention will be explained in detail below.

Examples of alkali metal hydroxides, alkaline earth metal hydroxides, metal carbonates, or metal bicarbonates that can be used in the present invention include lithium hydroxide, sodium hydroxide, potassium hydroxide, and calcium hydroxide. , lithium carbonate, sodium carbonate, potassium carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, etc. However, in the method of adding metal hydroxide, the pH of the polymerization system is adjusted to 5.0 to 9. Since it is difficult to control the temperature to .0, it is more preferable to use a metal salt of carbonate or a metal bicarbonate.

The total ion concentration of each alkali metal hydroxide, alkaline earth metal hydroxide, carbonate metal salt, and metal bicarbonate added to the aqueous medium is in the range of 0.0001 to 0.01 gram ion/l. It is preferable to coexist as shown in . If the ion concentration is less than 0.0001 gram ion/l, the effect will not be substantially expressed, and if the ion concentration exceeds 0.01 gram ion/l, the emulsion polymerization stability will be inhibited.
If the produced polymer is made into a molded article, the metal content will be high, which will adversely affect hot water whitening properties, which is not preferable.

In addition, it is expected that the pH of the polymerization system will shift to the alkaline side due to the addition of a strong or weak alkaline substance to the aqueous medium, but the pH of the polymerization system can be adjusted to 5.0 to 5.0 by adjusting the amount of the alkaline substance added. It should be adjusted to a range of 9.0. If the pH deviates from this range, the decomposition rate of the polymerization initiator will decrease, the amount of undecomposed polymerization initiator after the polymerization reaction will increase, and the heat resistance of the resulting remer will decrease. Furthermore, if the pH is significantly outside the range of 5.0 to 9.0, the emulsion polymerization system may be destroyed and agglomeration may occur, which is not preferable.

Monomers containing acrylic esters and/or methacrylic esters used in carrying out the present invention include acrylic acid or methacrylic esters of aliphatic, alicyclic, aromatic alcohols and phenols having 1 to 12 carbon atoms. or a mixture thereof, or a mixture with other copolymerizable monomers containing these.

Specific examples of acrylic or methacrylic esters of aliphatic, alicyclic, aromatic alcohols and phenols having 1 to 12 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, and (meth)acrylate. Propyl acid, (
butyl meth)acrylate, amyl(meth)acrylate,
Alkyl (meth)acrylates such as hexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, etc. Aminoalkyl (meth)acrylates such as hydroxyalkyl (meth)acrylate), N,N-trimethylaminoethyl (meth)acrylate, epoxyalkyl (meth)acrylates such as glycidyl (″′) acrylate, cyclohexyl ( Examples include meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, etc. Among these, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylate are particularly preferred. Monomers selected from 2-ethylhexyl acid, benzyl (meth)acrylate, etc. are preferred. Other copolymers that can be used in combination with the above acrylic esters and methacrylic esters include, for example, acrylic acid, α of methacrylic acid, itaconic acid, etc.
β-unsaturated acid, itaconic acid ester, acrylamide,
α, β-unsaturated acid amides and their derivatives such as methacrinolamide, α, β-unsaturated nitriles such as acrylonitrile and methacrylaterile, aromatic vinyl compounds such as styrene, vinyltoluene, α-methylstyrene, acetic acid Vinyl esters such as vinyl propionate, allyl compounds such as allyl acetate and allyl maleate, vinyl chloride, vinyl halides such as vinylidene chloride,
Monomers having two or more copolymerizable unsaturated bonds, such as (poly)ethylene glycol resin (meth)acrylate, allyl (meth)acrylate, triallyl (yne)
Compounds such as cyanurate and divinylbenzene can be mentioned.

Examples of soaps used as emulsifiers in the present invention include sulfuric acid ester salts and phosphoric acid ester salts of higher alcohols, dialkyl sulfoconolinates, alkylaryl sulfonates, α-olefin sulfonates, and the like. . The amount of these soaps used is in the range of 0.5 to 15 parts by weight per 100 parts by weight of water.

Polymerization initiators used in the practice of the present invention include water-soluble peroxides such as persulfates and percarbonates, hydrogen peroxide and ferrous salts, hydro-9-oxide and sodium formaldehyde sulfoxylate, etc. Examples include redox initiators represented by combinations, and the amount thereof used is generally in the range of 0.001 to 1.0 parts by weight per 100 parts by weight of the monomer.

The monomer/water ratio when carrying out aqueous emulsion polymerization is not particularly limited and is carried out in the range of about 115 to 1/1. Monomers may be added at once before polymerization, but depending on the purpose. may be added in portions or continuously during polymerization. The polymerization temperature can vary in various ranges depending on the type and composition of the monomers used, but it is usually carried out at 20 to 100°C. .

In Examples, the polymerization stability, the thermal stability of the produced polymer, and the hot water whitening resistance of the produced polymer film were determined by the following methods.

In the examples, parts and parts are by weight.

Polymerization Stability After the completion of the polymerization reaction, the aggregated polymer floating in the latex and the polymer attached to the stoneware wall were collected, dried and weighed, and the weight ratio relative to the charged monomer was determined.

Thermal stability: Melt In as shown in ASTM-D-
The dex value is determined by the ratio of the value after heating at 230°C for 5 minutes and the value after heating at 230°C for 30 minutes, that is, the MI value after heating at 230°C for 30 minutes/MI value after heating at 230°C for 5 minutes. displayed.

Warm water whitening resistance: Film molded to a thickness of 50μ is '20
The sample was placed on a wire mesh with a wire mesh size of 0.0 mm and 0.5 mm and immersed in water for 30 minutes, and changes in appearance were observed.

The display is as follows: ◎... No change in transparency O... Slightly cloudy Δ... Whitening is observed ×... Loss of clarity and opacity Also, in the examples, ■ indicates methyl methacrylate. ,
BuA is butyl acrylate, BD is 1,3-butylene dimethacrylate, AMA is allyl methacrylate, C
HP stands for cumene hydroperoxide and SFS stands for lysium formaldehyde sulfoxylate.

Example 1 A mixture consisting of the dispersion medium composition shown in Table 1 was charged into a reactor equipped with a stirrer, a thermometer, a nitrogen blowing tube, and a dropping bottle, and nitrogen gas was blown into the system while stirring the contents to remove oxygen from the system. After removal, the temperature was raised to 70°C, and kMA 1.6 parts BuA 8
part, B D 0.4 part, AMA 0.1 part and CHP
A mixture consisting of 0.04 parts was charged. The reaction was continued for 60 minutes at 70°C, followed by 1.5 parts of MMA, BuA22
．． 5 parts B D 1.0 parts, AMA 0.25 parts, CHP
Add 0.0125 parts over 60 minutes.

Furthermore, after reacting a mixture of 5 parts of MMA, 5 parts of BuA, and 1 part of AMA O, 52.25 parts of MMA, BuA
The outermost layer consisting of 2.75 parts of polymer was reacted to complete the polymerization reaction.

The obtained latex was cooled, then salted out using 5 parts of calcium chloride per 100 parts of the polymer, washed, dried, pelletized, and used as a sample for thermal stability measurement. In addition, since it could be easily formed into a 50μ film (using a retted sample using a conventional method), it was used as a hot water whitening sample. The evaluation results are shown in Table 2.

Experiment No. 6.7.8 is a polymerization stabilization method using boric acid and sodium carbonate in combination, and although the polymerization stability and thermal stability are improved, the hot water whitening resistance is deteriorated.

In addition, in experiment number 9.10, the silatex system was destroyed when excessive amounts of IJum and sodium carbonate were used. Experiment No. 11 was a case in which no polymerization stabilizer was used, and the polymerization was slightly unstable.Although the hot water whitening resistance was not bad, the thermal stability was poor.

Table 2 Example 2 Using the same reaction apparatus as in Example 1, a mixture consisting of the dispersion medium composition shown in Table 3 was charged, and after removing oxygen in the system using nitrogen gas, the temperature was raised to 70°C. , BuA 30 parts, A
A mixture consisting of 1.5 parts MA and 0.02 parts CHP was charged. After continuing the reaction at 70°C for 60 minutes, B
A mixture of 5 parts of uA, 5 parts of MMA, and 1 part of AMA O was reacted, and then an outermost layer polymer consisting of 55 parts of MMA, 0.3 parts of n-octyl mercaptan, and 0.3 parts of n-octyl mercaptan was reacted to complete the polymerization reaction.

The obtained latex was cooled, then salted out using 5 parts of calcium chloride per 100 parts of the polymer, washed, dried, heated, and then used as a sample for measuring thermal stability. Furthermore, since a 50μ film could be easily formed using the pelletized sample by a conventional method, it was used as a sample for measuring hot water whitening resistance. The evaluation results are shown in Table 4 ◎ Comparative Examples 6 to 9 are examples in which an excess or only a small amount of polymerization stabilizer was used υ, and Comparative Example 10 is an example in which no polymerization stabilizer was used at all. .

Claims (1)

[Claims] When polymerizing in an aqueous medium using an emulsifier containing a monomer containing an acrylic ester and/or a methacrylic ester as a main component and a sulfonic acid soap as a main component, water is added to the aqueous dispersion medium constituting the polymerization system. At least one ion selected from acid ions, carbonate ions, and bicarbonate ions is 0
．． Alkali metal hydroxides, alkaline earth metal hydroxides, and carbonic acid were added so that the concentration of An emulsion polymerization method characterized by the presence of a metal salt or metal bicarbonate.