JPH0441511A - Production of diene copolymer latex - Google Patents

Abstract

PURPOSE:To produce the title latex improved in adhesiveness, etc., and being useful for paper coating, etc., by emulsion-polymerizing a conjugated diene compound with an ethylenically unsaturated carboxylic acid and another monomer while continuously and gradually adding a chain transfer agent to the reaction system under specified conditions. CONSTITUTION:A process for emulsion-polymerizing 40-60wt.% monomer mixture of a mean particle diameter of 0.05-1mum comprising 5-90 wt.% conjugated diene compound (A), 0.2-15wt.% ethylenically unsaturated carboxylic acid (B) and a comonomer (C) in an aqueous medium in the presence of a chain transfer agent (D), a surfactant (E) and a radical polymerization initiator (F), wherein component D is continuously and gradually added to the reaction system in such an amount that the relationships of formulas I and II (wherein (x) is the amount (pts.wt.) of component D which is added per 100 pts.wt. above monomer mixture until the conversion reaches 70%, and (y) is the amount (pts.wt.) of component D which is added per 100 pts.wt. above monomer mixture during the period from the time when the addition of the above monomer mixture is completed to the time when the conversion reaches at least 85%) are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improved method for producing copolymer latex. More specifically, the present invention relates to a method for efficiently producing a copolymer latex with suitable post-performance properties as a binder for paper coating, carpet backing and binding, and fiber binding. .

Conventional technology Conventionally, synthetic copolymer latex has been used as a binder for paper coating, carpet backing, binder for legs, high leg for bonding fibers with non-woven fabrics and artificial leather, and adhesives for various materials. It is widely used as nato. When a copolymer latex is used for such purposes, the copolymer latex is required to have high adhesive strength and excellent water resistance and blistering resistance due to dry heating.

For example, coated paper uses kaolin, -1 carbonate, satin white, talc, titanium oxide, etc. on the surface of the base paper to improve the paper's printability and optical properties such as gloss. Coated with a paint whose main components are pigments, a copolymer latex as a binder, and a water-soluble polymer such as starch, casein, polyvinyl alcohol, or carboxymethylcellulose as a water-retaining agent or auxiliary binder. ,
As the copolymer latex, styrene-butadiene copolymer latex, so-called SB latex, which is obtained by emulsion polymerization of styrene and butadiene as main monomer components, has been widely used.

Incidentally, in recent years, the production of coated paper has increased significantly as demand for color-printed magazines, pamphlets, and advertisements has increased. In particular, with the trend toward higher speed printing in offset printing, the quality requirements for coated paper and pigment binders are becoming increasingly sophisticated. Improvement is strongly required. Moreover, this pick strength performance has a negative correlation with other print properties, such as wet shock strength, blister resistance, halftone dot reproducibility, etc., so improvements that balance these physical properties to a high level are required. requested.

Since these properties of coated paper are particularly strongly dependent on the performance of the SB latex used as a pigment binder, various studies have been made on the performance of the SB latex.

For example, it has been confirmed that the proportion of the insoluble portion of the copolymer latex film in solvents such as benzene, toluene, and tetrahydrofuran is the controlling factor for pick strength and blister resistance, and various studies have been conducted from this point of view. Specifically, by adjusting the composition and gel fraction of the copolymer in the latex to a specific range,
It has been proposed to exhibit excellent performance (Japanese Patent Publication No. 593598, Japanese Patent Publication No. 60-17879,
JP-A No. 58-4894). The gel fraction of this latex varies depending on various polymerization factors such as monomer composition and polymerization temperature, but a common and simple method for adjusting it to a desired level is to add a chain transfer agent.

However, when the gel fraction is adjusted by the amount of chain transfer agent, the pick strength of coated paper for boat fishing is highest when the gel fraction is in the range of 75 to 95% by weight for SB latex. On the other hand, it is recognized that the lower the gel fraction, the better the blister resistance is.In order to simultaneously improve both pick strength and blister resistance to a high level, the above-mentioned technology is is also not completely satisfactory.

On the other hand, a method has also been proposed in which the rate of addition of the chain transfer agent into the polymerization system is varied within the range where the addition of the chain transfer agent ends at the same time as the end of the addition of the monomers (Japanese Patent Publication No. 1983-1999-1).
8443, Japanese Patent Application Laid-open No. 61-63794). However, none of these methods is fully satisfactory for simultaneously improving both pick strength and blister resistance to a high level.

On the other hand, carpet back sizing adhesives are generally compositions of copolymer latex blended with fillers such as calcium carbonate or aluminum hydroxide and other additives such as thickeners, and are suitable for use in tufted carpets, In the production of needle punch carpets, etc., it is mainly used to prevent piles from falling off and to adhere to secondary base fabrics such as Noyute. Therefore, in this case, improving adhesive strength, which is the most important physical property of carpet, is one of the biggest technical challenges in this industry, and therefore, improvements are being considered from the aspect of blending copolymer latex and compositions. However, the reality is that a satisfactory level has not been obtained so far.

As described above, the conventional technology is unable to cope with the ever-increasing printing speed of coated paper, and there is a strong need for the emergence of copolymer latex as a binder that will enable the production of high-quality coated paper. Furthermore, copolymer latexes with high adhesive strength are also desired for carpets and adhesives.

Problems to be Solved by the Invention Under these circumstances, the present invention aims to improve the balance between the bulk strength and other properties of coated printing paper, and the adhesive strength of carpet back sizing and adhesives. This was done with the aim of providing a high-performance copolymer latex for improving the quality of the product.

Means for Solving the Problems As a result of intensive research to develop a copolymer latex having the above-mentioned preferred properties, the present inventors found that when producing a diene copolymer latex by emulsion polymerization,
A specific amount of chain transfer agent is continuously added to the polymerization system until the polymerization rate reaches a specific value, and then a specific amount of chain transfer agent is added to the polymerization system at a point after the end of the addition of the monomer, and the polymerization It was discovered that the objective could be achieved by continuously and sequentially adding the compound to the polymerization system until the ratio reached a specific value, and based on this knowledge, the present invention was completed.

That is, the present invention provides a method for producing a diene copolymer latex by emulsion polymerizing a conjugated diene compound, an ethylenically unsaturated carboxylic acid, and other copolymerizable monomers in an aqueous medium. Add X parts by weight of the chain transfer agent to 100 parts by weight of the total amount of the chain transfer agent until the polymerization rate reaches 70%, and further until the time after the addition of the monomer is completed and the polymerization rate reaches at least 85%. Provided is a method for producing a diene copolymer latex, characterized in that 7 parts by weight of a chain transfer agent are continuously and sequentially added into a polymerization system so that X and y satisfy the relationship of formula %. It is.

The present invention will be explained in detail below.

Examples of the chain transfer agent used in the present invention include alkyl mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, and mercaptoethanol;
Examples include thioglycolic acid esters, sulfides, and halogen compounds such as pentaerythritol tetrathioglycolate. These chain transfer agents are 1
One seed may be used, or two or more types may be used in combination.

Continuous sequential addition of a chain transfer agent in the present invention means that the chain transfer agent is continuously added to the reactor, and the addition rate must not be zero, but the addition rate must not change continuously. It doesn't have to be, and it can be intermittent.

It is important that the addition of the chain transfer agent begins at the beginning of polymerization, and ends after the monomer addition ends, and at a time when the polymerization rate is at least 85%. A more preferable point at which the addition of the chain transfer agent ends is:
This is the point at which the polymerization rate becomes 90% or more, and more preferably the point at which the polymerization rate becomes 90% or more.

Regarding the addition rate of the chain transfer agent, the total amount of monomers is 10
0 parts by weight, (1) X parts by weight until the polymerization rate reaches 70%, and (2) y until the time after the monomer addition is completed and the polymerization rate reaches at least 85%.
It is necessary to continuously and sequentially add I parts by weight into the polymerization system so that X and y satisfy the relationship of formula 0.

Unless the addition end point and addition rate of the chain transfer agent are set as described above, the balance between good pink strength and other properties, which is the object of the present invention, cannot be achieved.

Methods for adding the chain transfer agent include adding only the chain transfer agent alone to the polymerization vessel, adding the chain transfer agent after diluting it with a non-reactive solvent, and emulsifying the chain transfer agent in advance. One possible method is to make an aqueous dispersion and then add it. It is also possible to use a method in which a part of the chain transfer agent is mixed in advance with the monomer mixture, the addition of the mixture is terminated during polymerization, and the remaining chain transfer agent is subsequently added alone.

In the present invention, examples of the conjugated diene compound used include butadiene, isoprene, 2-chloro-1,3
-butadiene and the like. These conjugated diene compounds may be used alone or in combination of two or more, and the amount used is in the range of 5 to 90% by weight based on the weight of all monomers. is desirable. Furthermore, in the case of a copolymer latex for coated paper, a more preferable amount of the conjugated diene compound to be used is selected within the range of 20 to 70% by weight.

Examples of the ethylenically unsaturated carboxylic acids used in the present invention include monobasic acids such as acrylic acid, methacrylic acid, itaconic acid, and crotonic acid; dibasic carboxylic acids such as maleic acid, and fumaric acid; Examples include monoester. These ethylenically unsaturated carboxylic acids may be used alone or in combination of two or more, and the amount used is usually 0.2% by weight or more based on the weight of all monomers. , preferably 0.
It is selected in a range of 2 to 15% by weight.

Other copolymerizable monomers used in the present invention include aromatic monovinyl compounds, divinyl compounds, acrylic esters, methacrylic esters, vinyl cyanide compounds, and ethylenic amides.

As the aromatic monovinyl compound or divinyl compound,
Examples include styrene, a-methylstyrene, chlorostyrene, alkylstyrene, and divinylbenzene. Examples of acrylic esters and methacrylic esters include methinoethyl, propyl, butyl, 2-ethylhexyl, hydroxyethyl, and glycidyl esters of acrylic acid or methacrylic acid, and ethylene glycol diacrylate or dimethacrylate. Examples of vinyl cyanide compounds include acrylonitrile and methacrylaterile, and examples of ethylenic amides include acrylamide, methacrylamide, N-methylolacrylamide, and N-methylolmethacrylamide.

In addition to these monomers, vinyl esters such as vinyl acetate, vinyl chloride, vinyl halides such as vinylidene chloride, aminoethyl acrylate or methacrylate, dimethylaminoethyl acrylate or methacrylate, diethylaminoethyl acrylate or methacrylate, etc. Ethylenic amines, sodium styrene sulfonate, etc. can also be used.

One type of these copolymerizable monomers may be used, or two types of these copolymerizable monomers may be used.
You may use combinations of more than one species.

In the present invention, the copolymer latex is obtained by emulsion polymerization of the conjugated diene compound, ethylenically unsaturated carboxylic acid, and other copolymerizable monomers in an aqueous medium. This emulsion polymerization is not particularly limited as long as the addition of the chain transfer agent satisfies the above conditions, and conventionally known methods can be used.

The concentration of the copolymer in the copolymer latex is usually selected in the range of 40 to 60% by weight.

The average particle diameter of the copolymer latex in the present invention can be adjusted by the proportion of surfactant and seed latex used, and generally, the higher the proportion used, the smaller the average particle diameter of the resulting copolymer latex tends to be. There is. It is desirable that the average particle diameter is in the range of 0.05-1 .mu.m, preferably 0-07-0.3 .mu.m.

Examples of the surfactant include fatty acid soap:/, o
Anionic surfactants such as H soap, alkyl sulfonates, dialkylaryl sulfonates, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, polyoxyethylene alkylaryl sulfates,
Examples include nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, polyoxyethylene sorbitan fatty acid ester, and oxyethylene oquine propylene block copolymer. This surfactant is usually used as an anionic surfactant alone or as a mixed anionic/nonionic system, and the amount used is usually 0.0 based on the weight of the total monomer.
It is selected in a range of 5 to 2% by weight.

The radical polymerization initiator required to initiate polymerization is one that has the effect of causing addition polymerization of monomers by radical decomposition by heat or a reducing substance. Examples of such initiators include water-soluble or oil-soluble beroxonisulfate,
Peroxides, azobis compounds, etc., specifically potassium beroxonisulfate, sodium beloxonisulfate, ammonium beloxonisulfate, hydrogen peroxide, tert-butyl hydroperoxide, benzoyl peroxide, 2,2-azobisisobutyronitrile, cumene hydro Examples include peroxides, and among these, beroxonisulfate is particularly preferred. The amount of the polymerization initiator used is usually selected within the range of 0.2 to 1.5% by weight based on the weight of all monomers.

The polymerization temperature in this emulsion polymerization is usually 60 to 100°
C, but if it is desired to accelerate the polymerization rate or polymerize at a lower temperature, a reducing agent such as acidic sodium sulfite, ascorbic acid or its salts, erythorbic acid or its salts, or Rongalit may be used as a polymerization initiator. A so-called redox polymerization method, which is used in combination, can be employed.

In the present invention, various polymerization regulators such as sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, disodium hydrogen phosphate, etc. can be used as desired.
H regulators and various chelating agents such as sodium ethylenediaminetetraacetate can be added.

When the copolymer latex produced according to the present invention is used as a binder for paper coating paints, it is possible to use the commonly used method, for example, adding an inorganic pigment or inorganic/organic pigment to water in which a dispersant is dissolved. The copolymer latex is added and mixed together with a polymeric compound and various additives,
A method using a homogeneous dispersion can be adopted. This paper coating paint can be applied to base paper by a conventional method using various blade coaters, roll coaters, and the like.

Effects of the Invention According to the present invention, it is possible to easily create a high-performance copolymer latex that can further improve the balance between pink strength and other properties in coated printing papers, and the adhesive strength in carpet back sizing and adhesives. can be obtained.

Examples Next, the present invention will be explained in more detail with reference to examples.
The present invention is not limited in any way by these examples.

In addition, each characteristic was calculated|required as follows.

(1) Properties of copolymer latex (a) Polymerization rate Weigh the extracted reaction solution accurately, dry it at 130'O for 1 hour, weigh the remainder, and calculate the solid content using the following formula: do.

In addition, the charged solid content is calculated using the following formula.

Charged solid content (fr amount%) - From these, the polymerization rate is calculated using the following formula.

(2) Evaluation of paper coating performance (a) Blister resistance Printing ink (Webb Zett yellow, manufactured by Dainippon Ink Co., Ltd.) on both sides of coated paper using R1 printing tester (manufactured by Mei Seisakusho)
Print 0.3mQ. This printed coated paper is cut into a suitable size, the test piece is adjusted to a predetermined σ temperature, and immersed in a Noricon oil constant temperature bath to observe whether or not blisters occur. This test is conducted by changing the temperature of the constant temperature bath, and the temperatures at which Bliss 9-(7) occurs are compared.

The evaluation was performed using a 10-point evaluation method, and the better the blister resistance, the higher the score.

(b) Using a dry pink strength R1 printing tester, print ink (S
D Super Deluxe 50 Crimson B: Tanok value 18) 0.
Overprint 4mQ 5 times, trace the pinking that appears on the rubber roll onto another mount, and observe the situation. Evaluation was performed using a 10-point evaluation method, and the fewer the picking phenomenon, the higher the score.

Examples, Comparative Example 1.2 4 parts by weight of an aqueous dispersion of 0.04 µm diameter solid particles (25% by weight solid content) was placed in a pressure-resistant reaction vessel equipped with a stirring device and a temperature control jacket, and further 70 parts by weight of water, 0.2 parts by weight of sodium lauryl sulfate, and 2.5 parts by weight of fumaric acid were charged, the internal temperature was raised to 80°C, and then the monomer mixture shown in Table 1 and 15 parts by weight of water were charged. part by weight, an aqueous solution consisting of 1 part by weight of sodium beroxonisulfate, 0.2 part by weight of sodium hydroxide, and 0.1 part by weight of sodium lauryl sulfate were ignited at a constant flow rate over 4 hours and 5 hours, respectively. In addition, the chain transfer agents shown in Table 1 were used in Figure 1 (Example), @ Figure 2 (Comparative Example 1), and Figure 3.
It was added at the time shown in the figure (Comparative Example 2). Then, after 6 hours had passed from the start of polymerization, it was cooled, and the resulting copolymer latex was adjusted to a pn of 7 with sodium hydroxide, and unreacted monomers etc. were removed by a steam stripping method. It was filtered through mesh filter cloth. Note that all copolymer latexes were adjusted so that the final solid content concentration was 50% by weight.

Table 1 Application Examples The copolymer latex prepared in Example and Comparative Example 1.2 was evaluated for its performance as a paper coating binder. The results are shown in Table 4.

The coating material had the formulation shown in Table 2 and was prepared using a high-speed stirrer with an amount of water that gave a nonvolatile content concentration of 63% by weight. The pt+ of the paint was adjusted to 9.0 with ammonium water. Table 3 shows the conditions for preparing coated paper using this paint.

From Table 4, it is understood that the coated paper using the copolymer latex of the present invention as a binder has a high balance of bulk strength and other physical properties.

Table 2 Table 3 Note 1) “Ultra White 90” manufactured by Engelhard 2
) “Ultracoat” manufactured by Engelhard 3) “Niscallon #1500J4” manufactured by Sanki Seifun Co., Ltd. “Aron T-40J5 manufactured by Toagosei Kagaku Co.)” “Sumilets 63” manufactured by Sumitomo Chemical Co., Ltd.
6” 6) Nihon Shokuhin Kako Co., Ltd. r M S 4600J Table

[Brief explanation of drawings]

1, 2, and 3 are graphs showing the relationship between the time from the start of polymerization and the amount of chain transfer agent added in Examples, Comparative Example 1, and Comparative Example 2, respectively.

Claims (1)

[Claims] 1. In producing a diene copolymer latex by emulsion polymerizing a conjugated diene compound, an ethylenically unsaturated carboxylic acid, and other copolymerizable monomers in an aqueous medium, Polymerization rate is 70% based on 100 parts by weight of total amount
x parts by weight of the chain transfer agent until the point at which the monomer addition is completed, and the polymerization rate is at least 8.
y parts by weight of the chain transfer agent were continuously added to the polymerization system until the chain transfer agent reached 5%, so that x and y satisfied the following relationships: 1. A method for producing a diene copolymer latex, which comprises adding diene copolymer latex.