JP2744649B2 - Copolymer latex, coated paper and carpet using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a polymer latex for a paper coating paint, carpet backsizing and other binders.

<Conventional technology> Coated paper is used to improve the printability of paper and to improve optical characteristics such as gloss, and to apply kaolin clay, calcium carbonate, satin white, talc, titanium oxide, etc. It is coated with a paint containing a pigment, a polymer latex as a binder thereof, and a water-retaining polymer such as starch, polyvinyl alcohol, and carboxymethyl cellulose as a water retention agent or an auxiliary binder. Here, as a polymer latex as a binder, a styrene-butadiene-based polymer latex emulsion-polymerized with styrene and butadiene as main monomer components, a so-called BS latex, has been generally used.

By the way, production of coated paper has increased remarkably with the recent increase in demand for color printed magazines, pamphlets, and advertisements. On the other hand, in the printing of coated paper, the demand for high-speed printing is increasing due to the growing demand, and the required level of the quality is also becoming more sophisticated. Therefore, among the quality of the coated paper, particularly, improvement in ink pick resistance, so-called pick strength, is strongly demanded. However, this pick strength performance is negatively correlated with other print properties, such as wet pick strength, blister resistance, halftone dot reproducibility, and the like, and an improvement in balance is desired.

Since such a quality strongly depends on the design of the SB latex used as a pigment binder, various studies have been made so far. Among them, the gel fraction of the latex, that is, a polymer film formed by coagulating and depositing polymer particles by adding isopropyl alcohol or the like to a film formed by drying the latex, or separating and drying the polymer particles benzene and toluene Since it has been confirmed that the proportion of a portion insoluble in a solvent such as tetrahydrofuran or the like is a controlling factor of pick strength and blister resistance, various studies have been made from this aspect. That is, JP-B-59-3598, JP-B-60-17879 and JP-A-58-4894 show excellent performance by adjusting the latex to a specific range of polymer composition and gel fraction. It has been proposed to do so. In addition,
JP-A-62-117897 discloses that pick strength is excellent in blister resistance by mixing a low gel fraction latex and a high gel fraction latex having a specific polymer composition in a specific range of ratio. It is said that it can be.

The gel fraction of this latex varies depending on various polymerization factors such as monomer composition and polymerization temperature, but a method for adjusting this to a desired level is generally and easily added with a chain transfer agent, Conventionally, halogenated hydrocarbons represented by carbon tetrachloride, alkyl mercaptans represented by t- or n-dodecyl mercaptan, and sulfides have been mainly used.

By the way, the pick strength of the coated paper is higher even in the SB type latex even if its gel fraction is in the range of 75 to 95% by weight, whereas the blister resistance is better as the gel fraction is lower. Has been generally confirmed. Therefore, it is very difficult to simultaneously increase both the pick strength and the blister resistance to a high level, and in the past, it has been necessary to adjust the gel fraction of the latex in an appropriate range and compromise until now. Was.

The optimal butadiene fraction with the same pick strength is 40.
%, But the butadiene fraction most suitable for halftone dot reproducibility was 50% or more, and it was difficult to simultaneously increase both to a high level.

Similarly, the optimal butadiene fraction for wet pick strength is 34%
It was difficult to raise both at the same time to a high level.

On the other hand, an alkyl ester of thioglycolic acid is known as a chain transfer agent in emulsion polymerization as disclosed in JP-B-49-31736, but its effect on a latex containing a conjugated diene has not been known.

<Problems to be Solved by the Invention> With such a conventional technology, latex as a binder capable of producing high-quality coated paper cannot be adapted to recent high-speed printing. At present, it is strongly required to appear. In view of such a situation, the inventors of the present invention have requested that the pick strength and other performance, blister resistance, halftone dot reproducibility, wet pick strength, and the like of the current coated paper for printing be further enhanced. To provide a binder.

<Means for Solving the Problems> The present invention relates to a method for preparing 10 to 60% by weight of a conjugated diene, 1 to 15% by weight of an ethylenically unsaturated carboxylic acid, and 25 to 89% by weight of another monomer copolymerizable therewith. In producing a latex by emulsion polymerization, a general formula of 0.01 to 5.0% by weight based on 100% by weight of the monomer is used in the polymerization. (Where R represents an alkyl group having 2 to 18 carbon atoms) which solves the above problem by producing a copolymer latex characterized by using an alkyl thioglycolate represented by the following formula: is there.

 Hereinafter, the present invention will be described in detail.

In the emulsion polymerization for preparing the polymer latex of the present invention, 0.01 to 5.0% by weight of the general formula is used per 100% by weight of the monomer. (Where R represents an alkyl group having 2 to 18 carbon atoms) characterized in that an alkyl thioglycolate represented by the following formula is used as a chain transfer agent. The chain transfer agent can also be used in combination with other known chain transfer agents, and it may be desirable. However, in this case, in order to exhibit the effects shown in the present invention, the amount of the chain transfer agent other than the above-mentioned chain transfer agent is not more than the same amount of the above-mentioned chain transfer agent if it is an alkylthiol, and the above-mentioned chain transfer agent if it is a halogenated hydrocarbon. It is desirable to make it 5 times or less of the transfer agent. Examples of other well-known chain transfer agents include t-dodecyl mercaptan, n-dodecyl mercaptan, alkyl mercaptans such as mercaptoethanol, terpinolene, dipentene, halogenated hydrocarbons such as t-terpinene and carbon tetrachloride, sulfides and the like. Can be mentioned. Among them, t-dodecyl mercaptan is particularly desirable.

Any known method can be used for the method of using the chain transfer agent. That is, a batch addition method, a continuous addition method, an intermittent addition method, a concentration gradient addition method in which the addition rate is sequentially changed, and the like.

The latex polymer contains a monomer composed of 10 to 60% by weight of a conjugated diene, 1 to 15% by weight of an ethylenically unsaturated carboxylic acid, and 25 to 89% by weight of another monomer copolymerizable therewith. It is obtained by emulsion polymerization.

Conjugated dienes include butadiene, isoprene, 2
-Chloro-1,3-butadiene and the like, and it is essential that the used amount is 10 to 60%, more preferably 30 to 60%.
~ 45% by weight. In this range, it is possible to exhibit the highest pick strength, and if it is less than 10% by weight, the polymer becomes too brittle, and if it exceeds 60% by weight, it becomes too soft, giving a high pick strength in any case. Impossible.

Examples of the ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and the like. It is essential that the ethylenically unsaturated carboxylic acid be in the range of 1 to 8% by weight. If the amount is less than 1% by weight, the dispersion stability of the latex cannot be maintained at a high level, and various problems occur at the time of coating preparation and coating. Also, the pick strength is poor. If the content exceeds 15% by weight, the viscosity of the latex or paint will be too high, and the water resistance will be impaired.

Among the examples of other monomers, the most representative and effective one is an aromatic (di) vinyl compound,
Next, (meth) acrylic esters, vinyl cyanide compounds, ethylenic amide monomers and the like.

As aromatic (di) vinyl compounds, styrene, α-
Methyl styrene, chloro styrene, alkyl styrene,
And divinylbenzene.

(Meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hydroxyethyl (meth) acrylate, and , Glycidyl (meth) acrylate, ethylene glycol di (meth)
Acrylate and the like.

Examples of the vinyl cyanide compounds include acrylonitrile and methacrylonitrile.

Examples of the ethylenic amide monomer include (meth) acrylamide and N-methylol (meth) acrylamide.

In addition, vinyl esters such as vinyl acetate,
Examples thereof include vinyl halides such as vinyl chloride and vinylidene chloride, ethylenic amine monomers such as aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and diethylaminoethyl (meth) acrylate, and sodium styrene sulfonate. it can.

Next, the manufacturing method will be described. In the method for producing the copolymer latex of the present invention, it is produced by a conventionally known ordinary emulsion polymerization method. That is, water, a surfactant, a monomer, a radical polymerization initiator, and, if necessary, in a dispersion system containing other raw materials as a basic component, a production method in which the monomer is an aqueous dispersion of polymer particles, Generally, the polymer concentration is 40
It is in the range of ~ 60% by weight. The latex particle size can be adjusted by the use ratio of the surfactant and / or the seed latex. Generally, the higher the use ratio, the smaller the particle size of the produced latex.

Here, the preferable range of the particle diameter is 0.05 to 1 μm, and more preferably 0.07 to 0.3 μm.

Examples of the surfactant include anionic surfactants such as fatty acid soap, rosin acid soap, alkyl sulfonate, dialkylaryl sulfonate, alkyl sulfosuccinate, polyoxyethylene alkyl sulfate, and polyoxyethylene alkylaryl sulfate. And nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene sorbitan fatty acid ester, and oxyethylene oxypropylene block copolymer. The surfactant is usually used in the form of an anionic surfactant alone or an anionic / nonionic mixed system. The use ratio of the surfactant to the monomer is generally in the range of 0.05 to 2% by weight.

As a polymerization initiator, a radical decomposition is carried out in the presence of heat or a reducing substance to cause addition polymerization of a monomer, and a water-soluble or oil-soluble peroxodisulfate, a peroxide, an azobis compound, and the like. As potassium peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, 2,2-azobisisobutyronitrile, cumene hydroperoxide, and the like, In particular, peroxodisulfate is most preferably used. The ratio of the polymerization initiator used is usually 0.2 to the monomer.
~ 1.5% by weight. The polymerization temperature is generally in the range of 60 to 90 ° C., but if it is desired to accelerate the polymerization rate or to carry out the polymerization at a lower temperature, sodium bisulfite, ascorbic acid or a salt thereof, erythorbic acid or a salt thereof,
A so-called redox polymerization method in which a reducing agent such as Rongalite is used in combination with a polymerization initiator can be used.

Further, various polymerization regulators are often added as desired. For example, pH adjusters such as sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, sodium carbonate and disodium hydrogen phosphate, and various chelating agents such as sodium ethylenediaminetetraacetate.

In the case where the latex of the present invention is used as a binder for a paper coating composition, it can be carried out in a usual embodiment. That is, pigments in water in which the dispersant is dissolved,
In this embodiment, a latex is mixed with a water-soluble polymer and various additives to form a uniform dispersion. The paint can be applied to the base paper by a usual method such as a blade coater or a roll coater.

<Examples and Comparative Examples> Next, the present invention will be specifically described based on Examples and Comparative Examples, but it goes without saying that the present invention is not limited only to the following Examples. Parts and% in the text are based on weight.

(1) Preparation of polymer latex 4 parts of an aqueous dispersion of seed particles of 0.04 μm in diameter (seed solid concentration 25%) were placed in a pressure-resistant reaction vessel equipped with a stirring device and a temperature control jacket, and further 70 parts of water were added. ,
0.2 parts of sodium lauryl sulfate and 2.5 parts of fumaric acid were charged and the internal temperature was raised to 80 ° C. Then, an oily mixed solution comprising a monomer and a chain transfer agent shown in Table 1, 15 parts of water and 1 part of sodium peroxodisulfate , 0.2 parts of sodium hydroxide and 0.1 parts of sodium lauryl sulfate are added at a constant flow rate over 4 hours and 5 hours, respectively. Then, the temperature is kept at 80 ° C. for 1 hour and then cooled.
The polymer latex thus formed was adjusted to pH 7 with sodium hydroxide, then unreacted monomers were removed by a steam stripping method, and the mixture was filtered through a 200-mesh filter cloth. In addition, all polymer latexes were adjusted so that the solid concentration might be finally 50%, and subjected to the following tests.

The particle size and gel fraction of these polymer latexes were measured by the following methods, and the results are shown in Table 1.

<Measurement of particle size> Light scattering particle size analyzer (Model 600 manufactured by C-Nwood Inc.)
The average particle diameter of the polymer latex was measured according to 0).

<Measurement of Gel Fraction> A polymer latex was uniformly coated on a polypropylene film with a No. 26 wire bar, and dried in a dryer at 50 ° C. for 1 hour to form a film.

Next, peel off this latex film and use an analytical balance to
0.5 g is precisely weighed, immersed in a container containing 300 cc of toluene, and stirred with a shaker at room temperature for 6 hours.
Then, the content was filtered through a 325 mesh wire mesh that had been precisely weighed in advance, and the residue remaining on the wire mesh was dried in a 50 ° C.
Let dry for hours. The gel fraction is calculated by the following equation.

Gel fraction (%) = 100 x (weight of wire mesh residue after immersion in toluene) ÷ (weight of film before immersion in toluene) (2) Evaluation of paper coating performance The polymer latex prepared in (1) was used for paper coating. Performance evaluation as a binder was performed. The coating composition was prepared by a high-speed stirrer with the composition shown in Table 2 and an amount of water at which the non-volatile content was 63%. The pH of the paint was adjusted to 9.0 with aqueous ammonia. Table 3 shows the conditions for preparing coated paper using this paint.

Various physical properties of the prepared coated paper were evaluated by the following methods.

Blister resistance: 0.3 cc ink (Webb Zetrt yellow, manufactured by Dainippon Ink Co., Ltd.) on both sides of coated paper using RI printing tester (manufactured by Akira Seisakusho)
Print solid. The printed coated paper is cut into an appropriate size, and the test piece is immersed in a silicone oil thermostat adjusted to a predetermined temperature to observe whether blisters are generated. This test is performed by changing the temperature of the thermostatic bath, and the lowest temperature at which blister generation is recognized is determined.
The higher the temperature, the better the blister resistance.

Dry pick strength: Printing ink (manufactured by Toka Pigment Co., Ltd.)
SD Super Deluxe 50 crimson B; tack value 18) Perform 0.4cc overprinting 5 times, backing the picking condition that appeared on the rubber roll on another mount, and observe the situation. The evaluation was performed by a 10-point evaluation method, and the smaller the picking phenomenon, the higher the score.

Wet pick strength: Using a RI printing tester, moisten the surface of the coated paper with a water-absorbing roll, and then print 0.4 cc of printing ink (SD Super Deluxe 50 red B, tack value 18) once per print. The picking state that appears on the rubber roll is backed up by another backing, and the situation is observed. The evaluation was performed by a 10-point evaluation method, and the smaller the picking phenomenon, the higher the score.

Halftone dot reproducibility: Printing was performed using a Ministry of Finance Gravure testing machine, and the dot loss rate was counted. The evaluation was performed by a 10-point evaluation method, and the smaller the missing rate, the higher the score.

Table 4 shows the test results of Examples and Comparative Examples. According to this, it is understood that the coated paper using the latex of the present invention as a binder has a highly balanced pick strength and other physical properties.

(3) Carpet backsizing performance evaluation The polymer latex prepared in (1) was evaluated as a carpet backsizing binder. The adhesive paint was prepared by a high-speed stirrer with the composition shown in Table 5 and the amount of water at which the non-volatile content was 70%.
Table 6 shows the conditions for preparing carpets using this paint.

The peel strength and thread pulling force of the prepared carpet were evaluated by the following methods.

Peel strength: According to JIS L-1021. The higher the average, the better.

Thread removal strength: According to JIS L-1021. The higher the average, the better.

Table 7 shows test results as examples and comparative examples. According to this, it is understood that the carpet using the latex of the present invention as a binder has a highly improved peeling strength and thread removal strength.

<Effect of the Invention> The polymer latex of the present invention exhibits excellent adhesiveness, and in particular, as a binder for paper coating, in producing coated paper having excellent ink pick resistance in printing and other physical properties, and carpet backsizing. It is useful as a binder for plastics.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI D06M 15/693

Claims (8)

(57) [Claims] 1. A copolymer obtained by emulsion polymerization from 10 to 60% by weight of a conjugated diene, 1 to 15% by weight of an ethylenically unsaturated carboxylic acid and 25 to 89% by weight of other monomers copolymerizable therewith. Latex, which is polymerized in the general formula of 0.01 to 5.0% by weight based on 100% by weight of the monomer. (Wherein, R represents an alkyl group having 2 to 18 carbon atoms). A copolymer latex using an alkyl thioglycolate represented by the formula (1) as a chain transfer agent. 2. An alkyl group R added to thioglycolic acid
The copolymer latex according to claim 1, wherein is ethylhexyl. 3. The copolymer latex according to claim 1, wherein an alkylthiol and / or a halogenated hydrocarbon are used in combination as a chain transfer agent. 4. The copolymer latex according to claim 3, wherein the chain transfer agent used in combination is t-dodecyl mercaptan. 5. A method for adding a chain transfer agent, comprising:
5. The copolymer latex according to claim 1, wherein the copolymer latex is a continuous addition method, an intermittent addition method, or a concentration gradient addition method in which the addition rate is sequentially changed. 6. A method for adding a monomer in a batch pre-addition method, a continuous addition method, an intermittent addition method, a concentration gradient addition method in which the addition rate is sequentially changed, and a method in which a monomer component is changed stepwise. Multi-stage addition method, or claim 1 is a power feed addition method in which the monomer component is continuously changed.
2, 3, 4, or 5 copolymer latex. 7. Coated paper using the copolymer latex according to claim 1, 2, 3, 4, 5, or 6 as a binder for paper coating. 8. A carpet using the copolymer latex of claim 1, 2, 3, 4, 5, or 6 as a binder for backsizing.