JP2007145990A - Latex and film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a latex which has a good adhesion to various kinds of substrates and exhibits high water resistance and gloss, when processed into a film. <P>SOLUTION: The latex is obtained by polymerizing the monomer in the presence of a neutralized product of an alkali-soluble copolymer. The alkali-soluble copolymer contains a water-soluble polymer compound having an alcoholic hydroxyl group. The content of the gel portion of the latex particles constituting the latex is ≥50 wt.% to 100 wt.% of the total latex particles. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a latex obtained by polymerizing a monomer in the presence of a neutralized product of an alkali-soluble copolymer, and has good adhesiveness to various substrates when formed into a film. The present invention relates to a latex having high water resistance and gloss.

  Usually, a latex is obtained by polymerizing a monomer in an aqueous medium in the presence of an emulsifier. However, when the latex thus obtained is made into a film, there is a problem that the water resistance is poor. In order to solve this problem, it has been proposed to use a neutralized product of an alkali-soluble copolymer instead of an emulsifier as a dispersion stabilizer.

  The alkali-soluble copolymer is a copolymer that becomes soluble in an aqueous medium by the action of an alkali, and is usually used as an aqueous solution by neutralization with a basic substance. Examples of such an alkali-soluble copolymer include a copolymer obtained by polymerization in an organic solvent such as lower alcohols and ketones or a mixed solvent of glycols and water (for example, Patent Document 1), lauryl sulfate. Water in which a polymerizable emulsifier such as a copolymer obtained by emulsion polymerization in an aqueous medium in which a non-polymerizable emulsifier such as sodium is dissolved (for example, Patent Document 2), polyoxyethylene alkylpropenyl phenyl ether sulfate ammonium, etc. is dissolved A copolymer obtained by emulsion polymerization in a medium (for example, Patent Document 3) is known.

  However, in patent document 1, since the organic solvent was used when obtaining an alkali-soluble copolymer, there existed the following problems. That is, when such a copolymer is used as a dispersion stabilizer, there is a problem that the deorganic solvent becomes insufficient and the dispersion stability at the time of polymerization is reduced and a solidified product is generated. There was a problem that polymerization was inhibited due to the transfer effect.

  Further, as in Patent Documents 2 and 3, when an alkali-soluble copolymer produced using a non-polymerizable emulsifier or a polymerizable emulsifier is used as a dispersion stabilizer, the water resistance of the resulting film is: Although improved to some extent, it was still insufficient.

JP-A-57-108103 Japanese Patent Laid-Open No. 4-7309 Japanese Patent Laid-Open No. 6-271777

  The present invention has been made in view of such a situation, has a good adhesion to various substrates, and has a high water resistance and gloss when formed into a film, and a coating of this latex. It aims at providing the film obtained by doing.

  As a result of intensive studies to achieve the above object, the present inventors have found that the alkali-soluble copolymer in the latex obtained by polymerizing the monomer in the presence of a neutralized product of the alkali-soluble copolymer. It has been found that the above object can be achieved by containing a water-soluble polymer compound containing an alcoholic hydroxyl group in a polymer and controlling the gel content in latex particles constituting the latex within a predetermined range. The present invention has been completed.

That is, the latex according to the present invention is a latex obtained by polymerizing a monomer in the presence of a neutralized product of an alkali-soluble copolymer,
The alkali-soluble copolymer contains an alcoholic hydroxyl group-containing water-soluble polymer compound,
The latex content of the latex particles constituting the latex is 50% by weight or more based on 100% by weight of the entire latex particles.

Preferably, the ratio of the neutralized product of the alkali-soluble copolymer to 10 parts by weight of the monomer is 10 to 40 parts by weight.
Preferably, the monomer contains a crosslinkable monomer.
Preferably, the ratio of the water-soluble polymer compound contained in the alkali-soluble copolymer is 2 to 20 times that of the crosslinkable monomer by weight.
Preferably, the latex further contains an inorganic pigment.

  The film according to the present invention is a film formed by applying any of the above latexes.

According to the present invention, it is possible to provide a latex having good adhesion to various substrates and having high water resistance and gloss when formed into a film. Furthermore, according to the present invention, it is also possible to provide a film obtained by applying this latex and having the above characteristics.
In the present invention, the term “latex” is a concept including a latex composition and a water-based paint containing latex particles constituting the latex and materials other than water (for example, inorganic pigments).

  Hereinafter, the latex which concerns on this invention and the film obtained by apply | coating the latex of this invention are demonstrated in detail.

  The latex of the present invention is produced by polymerizing the monomer (B) in the presence of a neutralized product of the alkali-soluble copolymer (A).

Neutralized product of alkali-soluble copolymer (A) The neutralized product of the alkali-soluble copolymer (A) used in the present invention is obtained by neutralizing an alkali-soluble copolymer with a basic substance. It is.
The alkali-soluble copolymer (A) according to the present invention contains at least an alcoholic hydroxyl group-containing water-soluble polymer compound (a1), preferably in the presence of the alcoholic hydroxyl group-containing water-soluble polymer compound (a1). , Obtained by polymerizing a monomer mixture (a2) for an alkali-soluble copolymer comprising an ethylenically unsaturated carboxylic acid monomer and another monomer copolymerizable therewith. .

  The alcoholic hydroxyl group-containing water-soluble polymer compound (a1) means a water-soluble polymer compound containing 5 to 25 alcoholic hydroxyl groups per 1,000 molecular weight. Examples of the alcoholic hydroxyl group-containing water-soluble polymer compound (a1) include vinyl alcohol polymers such as polyvinyl alcohol and various modified products thereof; co-polymerization of vinyl acetate and acrylic acid, methacrylic acid or maleic anhydride Saponified products of coalescence; cellulose derivatives such as alkyl cellulose, hydroxyalkyl cellulose, alkyl hydroxyalkyl cellulose; starch derivatives such as alkyl starch, carboxymethyl starch and oxidized starch; gum arabic, tragacanth gum; polyalkylene glycol;

  Of these, vinyl alcohol polymers are preferred from the viewpoint of easy availability of industrially stable products, and in particular, cation-modified vinyl alcohol polymers having a cationic group such as a quaternary ammonium salt in the side chain. Is preferred. The molecular weight of the alcoholic hydroxyl group-containing water-soluble polymer compound (a1) is not particularly limited, but is 10,000 to 500,000, preferably 20,000 to 150,000. If the molecular weight is too small, the dispersion stabilizing effect may be lowered. On the other hand, if the molecular weight is too large, the viscosity at the time of polymerization becomes high and the polymerization may be difficult.

  The ratio of the alcoholic hydroxyl group-containing water-soluble polymer (a1) is determined by the addition of the crosslinkable monomer contained in the monomer (B) that is polymerized in the presence of a neutralized product of the alkali-soluble copolymer described later. It is preferable to determine the relationship with the amount. Specifically, the weight ratio with respect to the crosslinkable monomer (B) is preferably 2 to 20 times, more preferably 3 to 15 times. If the amount of the alcoholic hydroxyl group-containing water-soluble polymer (a1) is too small, the dispersion stabilizing effect is lowered, aggregates are generated during polymerization, and the adhesion, glossiness, and water resistance of the resulting film tend to deteriorate. is there. On the other hand, when the amount is too large, the viscosity at the time of polymerization becomes high, the polymerization becomes difficult, and the adhesion, gloss and water resistance of the resulting film tend to deteriorate.

  The ratio of the alcoholic hydroxyl group-containing water-soluble polymer (a1) to the monomer mixture (a2) for the alkali-soluble copolymer is not particularly limited, but is preferably based on 100 parts by weight of the monomer mixture. Is 0.2 to 15 parts by weight, more preferably 0.8 to 5 parts by weight.

The ethylenically unsaturated carboxylic acid monomer is not particularly limited, and examples thereof include ethylenically unsaturated monocarboxylic acid monomers such as acrylic acid and methacrylic acid; itaconic acid, maleic acid, fumaric acid, butenetricarboxylic acid, and the like. Ethylenically unsaturated polyvalent carboxylic acid monomers; partial ester monomers of ethylenically unsaturated polyvalent carboxylic acids such as monobutyl fumarate, monobutyl maleate, mono 2-hydroxypropyl maleate; maleic anhydride, anhydrous And polycarboxylic acid anhydrides such as citraconic acid. These monomers can be used alone or in combination of two or more.
Among these ethylenically unsaturated acid monomers, (meth) acrylic acid [meaning methacrylic acid and / or acrylic acid. The same applies to methyl (meth) acrylate. An ethylenically unsaturated monocarboxylic acid such as

  The amount of the ethylenically unsaturated carboxylic acid monomer used is preferably 5 to 80% by weight, more preferably 10 to 50% by weight, based on 100% by weight of the whole monomer mixture (a2). When there are too few ethylenically unsaturated carboxylic acid monomers, the obtained copolymer may not become soluble in an alkali. On the other hand, if the amount is too large, the dispersion stabilizing effect may be reduced.

  Other monomers that can be copolymerized with the ethylenically unsaturated carboxylic acid monomer are not particularly limited, and for example, aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, and chlorostyrene; Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate , N-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, (meth) acryl Ethylenically unsaturated carboxylic acid monomer such as glycidyl acid; vinyl sulfonic acid, methyl vinyl sulfo Sulfonic acid group-containing ethylenically unsaturated monomers such as acid, styrene sulfonic acid and sodium styrene sulfonate; cyano group-containing ethylenically unsaturated monomers such as (meth) acrylonitrile; ethylenically unsaturated monomers such as allyl glycidyl ether Saturated glycidyl ether monomers; ethylenically unsaturated amide monomers such as (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide; 1,3-butadiene, isoprene, 2,3 -Conjugated diene monomers such as dimethyl-1,3-butadiene and 1,3-pentadiene; carboxylic acid vinyl esters such as vinyl acetate; These monomers can be used alone or in combination of two or more.

  The amount of other copolymerizable monomers used is preferably 20 to 95% by weight, more preferably 50 to 90% by weight, based on 100% by weight of the whole monomer mixture (a2).

  Of the monomer mixture (a2) used for the production of the alkali-soluble copolymer, a monomer having a relatively low solubility in water, that is, a monomer having a solubility in 100 g of water at 20 ° C. of less than 0.2 g. The amount of the monomer used is preferably 30% by weight or less. If the amount is too large, the resulting copolymer may not be soluble in alkali.

  The alkali-soluble copolymer (A) includes an ethylenically unsaturated carboxylic acid monomer and other monomers copolymerizable therewith in the presence of the above-mentioned alcoholic hydroxyl group-containing water-soluble polymer (a1). The monomer mixture (a2) consisting of can be obtained by polymerization in an aqueous medium. At this time, a method in which the alcoholic hydroxyl group-containing water-soluble polymer and the monomer mixture are collectively added to the reactor before the start of polymerization and then polymerized may be employed, or before the start of polymerization. Alternatively, a method may be employed in which only a part is added and divided addition or continuous addition is performed after the start of polymerization. In addition, in the case of divided addition or continuous addition, the addition amount and the addition time may be adjusted as appropriate. For example, the addition amount is made uniform, the addition time is made constant, or the addition amount and the addition time are polymerized. It can be changed according to the progress stage.

  The alcoholic hydroxyl group-containing water-soluble polymer compound (a1) and the monomer mixture (a2) may be separately added to the reactor, or these may be dispersed in water in advance to obtain a dispersion. It may be added to the reactor. Among these addition methods, a method of dispersing in water in advance and dividing or continuously adding to the reactor as a dispersion is preferable. By adopting such a method, the chain distribution of the ethylenically unsaturated acid monomer in the polymer chain in the obtained alkali-soluble copolymer can be made uniform.

  Alternatively, when the alcoholic hydroxyl group-containing water-soluble polymer compound (a1) and the monomer mixture (a2) are added separately, it is desirable to start both additions almost simultaneously. If only a large amount of the monomer mixture is added first, aggregates are likely to be generated. On the other hand, when only a large amount of the alcoholic hydroxyl group-containing water-soluble polymer compound is added in advance, the polymerization system thickens or aggregates are easily generated. The addition of both does not necessarily have to be at the same time, but it is desirable that the addition be almost the same.

  The polymerization initiator for polymerizing the monomer mixture (a2) for the alkali-soluble copolymer is not particularly limited, and examples thereof include sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and peroxidation. Inorganic peroxides such as hydrogen; diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, di-t-butyl peroxide, iso And organic peroxides such as butyryl peroxide and benzoyl peroxide; azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, and methyl azobisisobutyrate; These polymerization initiators can be used alone or in combination of two or more. The amount of the polymerization initiator used varies depending on the type, but is 0.2 to 15 parts by weight, preferably 0.8 to 5 parts by weight, based on 100 parts by weight of the entire monomer mixture for the alkali-soluble copolymer. It is.

  These polymerization initiators can also be used as a redox polymerization initiator in combination with a reducing agent. The reducing agent used in this case is not particularly limited, and examples thereof include compounds containing metal ions in a reduced state such as ferrous sulfate and cuprous naphthenate; sulfonic acid compounds such as sodium methanesulfonate; dimethyl Amine compounds such as aniline; and the like. These reducing agents can be used alone or in combination of two or more. Although the usage-amount of a reducing agent changes with the kinds, Preferably it is 0.03-10 weight part with respect to 1 weight part of polymerization initiators.

  In the production of the alkali-soluble copolymer, a chain transfer agent can be used as necessary. Although it does not specifically limit as a chain transfer agent, From the viewpoint of the efficiency of chain transfer, the compound which has a mercapto group is preferable. Among them, particularly preferred are alkyl mercaptans such as n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, octyl thioglycolate, 3-mercaptopropionic acid and the like, which are compounds having 20 or less carbon atoms.

  When using a chain transfer agent, the addition amount is preferably 1 to 15 parts by weight, more preferably 5 to 12 parts by weight, based on 100 parts by weight of the whole monomer mixture (a2) for the alkali-soluble copolymer. Part. When the addition amount of the chain transfer agent is too small, the viscosity after neutralization tends to be high and handling tends to be difficult. On the other hand, when the amount is too large, the molecular weight of the resulting polymer is remarkably lowered, and it does not function as a dispersion stabilizer. The method of adding the chain transfer agent to the polymerization system is not particularly limited, and a method of batch addition may be adopted, or a method of adding intermittently or continuously may be adopted.

  The polymerization temperature when producing the alkali-soluble copolymer is preferably 0 to 100 ° C, more preferably 30 to 90 ° C.

And the neutralized product of an alkali-soluble copolymer (A) can be obtained by neutralizing the alkali-soluble copolymer (A) manufactured as mentioned above with a basic substance.
The basic substance used for neutralizing the alkali-soluble copolymer (A) is not particularly limited, and examples thereof include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; calcium hydroxide and hydroxide. Examples include alkaline earth metal hydroxides such as magnesium; ammonia; amines such as triethylamine and triethanolamine; and the like, and mixtures thereof. Of these, ammonia is preferred.

  In addition, the neutralization degree of the neutralized product of the alkali-soluble copolymer (A) used in the present invention is not particularly limited, and usually the neutralization degree (base to the molar equivalent of the ethylenically unsaturated acid monomer). The molar equivalent of the active substance) is 70% or more, preferably 95% or more.

Polymerization of the monomer (B) in the presence of the neutralized product of the alkali-soluble copolymer (A) Then, in the presence of the neutralized product of the alkali-soluble copolymer (A) obtained above, The latex of the present invention is obtained by polymerizing the monomer (B).
Although it does not specifically limit as a monomer (B) for superposing | polymerizing in presence of the neutralized material of an alkali-soluble copolymer, For example, aromatic vinyl, such as styrene, (alpha) -methylstyrene, vinyl toluene, chlorostyrene, etc. Monomer; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, n-amyl (meth) acrylate, (meta ) Isoamyl acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, Ethylenically unsaturated carboxylic acid ester monomers such as (meth) acrylic acid glycidyl; (meth) acrylonitrile Cyano group-containing ethylenically unsaturated monomers; ethylenically unsaturated glycidyl ether monomers such as allyl glycidyl ether; ethylenically unsaturated amide monomers such as (meth) acrylamide and N-methylol (meth) acrylamide; Conjugated diene monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene; carboxylic acid vinyl esters such as vinyl acetate; acrylic acid, methacrylic acid, fumaric acid And ethylenically unsaturated carboxylic acid monomers such as maleic acid and monoethyl maleate; and crosslinkable monomers such as divinylbenzene, ethylene glycol di (meth) acrylate and tetraethylene glycol di (meth) acrylate. These monomers can be used alone or in combination of two or more.

  In the present invention, among the above monomers, it is particularly preferable to include a crosslinkable monomer such as divinylbenzene, ethylene glycol di (meth) acrylate, or tetraethylene glycol di (meth) acrylate. By containing these crosslinkable monomers, the gel content in the latex can be set to a desired range, and as a result, adhesion and water resistance when formed into a film can be improved. The content of the crosslinkable monomer is preferably 0.05 to 1.0 part by weight, more preferably 0.1 to 0.8 part by weight with respect to 100 parts by weight of the whole monomer. If the content of the crosslinkable monomer is too small, the above effects tend not to be obtained. On the other hand, if it is too much, film formation becomes difficult.

  Moreover, it is preferable to make content of a crosslinkable monomer into the following ranges in relation to content of the above-mentioned alcoholic hydroxyl group containing water-soluble polymer compound (a1). That is, the ratio of the alcoholic hydroxyl group-containing water-soluble polymer compound is preferably 2 to 20 times, more preferably 3 to 15 times by weight with respect to the crosslinkable monomer.

  The ratio between the neutralized product of the alkali-soluble copolymer (A) and the monomer (B) polymerized in the presence of the neutralized product is preferably set in the following range. That is, the ratio of the neutralized product of the alkali-soluble copolymer (A) to 100 parts by weight of the monomer is preferably 10 to 40 parts by weight, more preferably 20 to 35 parts by weight. When the neutralized product of the alkali-soluble copolymer is too small, the effect of dispersing and dispersing the monomer is lowered, aggregates are generated, and latex may not be stably obtained. On the other hand, when the amount is too large, the viscosity of the obtained latex becomes high and handling may be difficult, or the water resistance of the obtained film may be deteriorated.

  The latex of the present invention can be obtained by polymerizing the monomer (B) in an aqueous medium in the presence of a neutralized product of the alkali-soluble copolymer (A). At this time, a method may be employed in which the neutralized product of the alkali-soluble copolymer (A) and the monomer (B) are collectively added to the reactor before the polymerization is started and then polymerized. Alternatively, a method may be adopted in which only a part of the neutralized product and the monomer is added before the start of polymerization, and then added in portions or continuously after the start of the polymerization. In addition, in the case of divided addition or continuous addition, the addition amount and the addition timing may be appropriately adjusted. For example, the addition amount is made uniform, the addition timing is made constant, or these are added to the progress stage of polymerization. It can be changed accordingly.

  The neutralized product of the alkali-soluble copolymer (A) and the monomer (B) may be added separately to the reactor, or they may be dispersed in water in advance to form a dispersion. It may be added to the vessel. When the neutralized product of the alkali-soluble copolymer and the monomer are added separately, it is desirable to start both additions almost simultaneously. If only a monomer is added in a large amount first, aggregates are likely to be generated. On the other hand, when only a neutralized product of the alkali-soluble copolymer is added in a large amount in advance, the polymerization system is thickened or aggregates are easily generated. The addition of both does not necessarily have to be at the same time, but it is desirable that the addition be almost the same.

  The temperature at which the monomer (B) is polymerized is preferably 0 to 100 ° C, more preferably 30 to 90 ° C.

  The latex of the present invention thus obtained has a gel content of latex particles constituting the latex of 50% by weight or more, preferably 55% by weight or more, based on 100% by weight of the entire latex particles. More preferably, it is controlled to 70% by weight or more. By making the gel content of the latex particles in the above range, when it is formed into a film, the adhesion to various substrates can be improved, and the gloss and water resistance of the resulting film can be improved. In addition, content of the gel part of latex particle can be calculated | required with the following method, for example. That is, first, a latex is formed into a film, and then the obtained film is immersed in methyl ethyl ketone (MEK) at a temperature of 20 ° C. for 48 hours. And content of a gel part can be calculated | required from the film weight before being immersed in MEK, and the film weight after being immersed.

  In addition, the latex of the present invention comprises a step of obtaining a neutralized product of an alkali-soluble copolymer (A) prepared in advance and further polymerizing the monomer (B) in the presence of this neutralized product. It is obtained through the process. Therefore, the latex of the present invention has a structure having a part mainly containing the alkali-soluble copolymer (A) and a part mainly containing the polymer of the monomer (B). In general, it will have two glass transition temperatures. Each of these parts forms a core-shell structure in which the part mainly containing the polymer of the monomer (B) is the core and the part mainly containing the alkali-soluble copolymer (A) is the shell. Alternatively, the portion mainly containing the alkali-soluble copolymer (A) is uniformly dispersed in the portion mainly containing the polymer of the monomer (B). May be.

  The latex of the present invention may contain various inorganic pigments as necessary to form a water-based paint. Such inorganic pigments are not particularly limited, and examples thereof include clay, talc, kaolin, aluminum hydroxide, calcium carbonate, titanium oxide, barium sulfate, zinc oxide, satin white, silica, mica and the like. Although content of an inorganic pigment is not specifically limited, Preferably it is 100-400 weight part with respect to 100 weight part of solid content contained in latex, More preferably, it is 150-300 weight part. According to the latex of the present invention, even when an inorganic pigment is contained to form an aqueous paint, a paint having excellent dispersibility, storage stability, and foam suppression can be obtained.

  The latex of the present invention thus obtained can be obtained by applying various substrates (for example, paper, plastic film, inorganic substrate, metal substrate) by a brush coating method, a dipping method, a spray method, a roll coater method, a doctor blade method or the like. Etc.), and then dried at room temperature or with warm air to form a film. Since the film thus obtained has high adhesion to various substrates and is excellent in gloss and water resistance, it can be suitably used for various applications requiring such performance.

  The present invention will be specifically described below with reference to examples and comparative examples. [Part] and [%] in these examples are based on weight unless otherwise specified. However, the present invention is not limited only to these examples. In addition, evaluation of the latex, the water-based paint containing an inorganic pigment, and the film obtained using these was performed by the following method.

Gel content in latex First, latex having a solid content adjusted to 30% was cast on a framed glass plate, and then allowed to stand at 25 ° C. for 4 days to form a film. Next, a certain amount of the obtained film was precisely weighed (weight W ₀ ), placed in an 80 mesh wire netting basket, and immersed in methyl ethyl ketone (MEK) at a temperature of 20 ° C. for 48 hours. Then, the immersed basket was pulled up and vacuum dried at 25 ° C. for 2 days, and then the amount of the latex film remaining in the basket without being dissolved in MEK was precisely weighed (weight W ₁ ). Finally, the gel content was determined from the obtained weights W ₀ and W _{1 according} to the following formula (1).
Gel content (% by weight) = (W ₁ / W ₀ ) × 100 (1)

Adhesive First, apply latex adjusted to a solid content concentration of 30% on a mortar plate, PVC plate, PET plate, ABS plate and aluminum plate in an amount of 100 g / m ² and leave at room temperature for 24 hours. Was dried into a film. Next, the adhesion of the obtained film was evaluated by a cross-cut method based on JIS K5600. Specifically, first, a total of 100 squares having a size of 1 mm × 1 mm were engraved on the coating film with a cutter knife on the obtained film. Next, a cellophane tape having a width of 25 mm was sufficiently pressed and pasted on the obtained grid, and then the cellophane tape was peeled off. As a result, the number of eyes remaining without omission was measured and evaluated according to the following criteria.
◎: 100 pieces ○: 99 to 90 pieces △: 89 to 80 pieces ×: 79 pieces or less

Glossiness First, a latex whose solid content concentration is adjusted to 30% is applied on a commercially available coated paper (basis weight 86 g / m ² , white paper gloss 20%) in an amount of 5 g / m ² and dried. Then, it was converted into a film and then conditioned under conditions of 23 ° C., 50% humidity and 24 hours. Next, for the obtained film, using a gloss meter (GM-26D, manufactured by Murakami Color Co., Ltd.), the reflectance (%) of light on the surface of the coated paper was measured under the conditions of an incident angle of 75 ° and a reflection angle of 75 °. It was measured. The greater the reflectivity, the better the gloss.

A latex whose water-resistant solid content is adjusted to 30% is applied on a glass plate in an amount of 100 g / m ² and dried to form a film. Thereafter, the condition is 23 ° C., humidity 50%, 24 hours. Was conditioned. Next, the obtained film (10 cm × 10 cm) was immersed in tap water at 23 ° C. for 10 days to perform a water resistance test of the latex film. Based on the number of blisters (blisters), the evaluation was as follows. The smaller the number of blisters, the better the water resistance.
A: 0 blister (no change)
○: Blister 1 to 5 △: Blister 6 to 15 ×: Blister 16 to 20 ××: Blister 21 or more

Storage Stability of Water-Based Paint First, the viscosity at 23 ° C. of an aqueous paint containing an inorganic pigment was measured using a B-type viscometer. Next, the paint was stored at 50 ° C. for 30 days, and then cooled again to 23 ° C., and the paint viscosity was measured. The difference in paint viscosity before and after storage was determined as an absolute value, and the ratio of the difference in paint viscosity before and after storage to the paint viscosity before storage was determined according to the following formula (2). Then, the obtained results were evaluated according to the following criteria.
Viscosity change rate (%) = (| viscosity after storage−viscosity before storage | / viscosity before storage) × 100 (2)
○: Viscosity change rate of less than 10% Δ: Viscosity change rate of 10% or more and less than 20% ×: Viscosity change rate of 20% or more

Water resistance of aqueous paint First, an aqueous paint containing an inorganic pigment is applied on a glass plate with a thickness of 250 μm using an applicator, and then dried under conditions of 23 ° C., humidity 50%, 72 hours. And the sample for a measurement which consists of a glass plate and a film was obtained by forming into a film. Subsequently, this sample was immersed in water for 24 hours, and then the sample was taken out of water, the state of the coating film surface was observed, and the water resistance was evaluated by judging according to the following criteria.
○: There is no change in the state of the coating film surface as compared to before immersion in water.
(Triangle | delta): The location where the coating film swells with water and the glass plate and the coating film have peeled exists partially.
X: The coating film peeled from the glass plate over almost the entire surface.

Pigment dispersibility of water-based paint (linear method)
About the water-based paint containing an inorganic pigment, based on JIS K5400 4.7.2 (linear method), the paint dispersion degree was measured using a crush gauge, and in this example, less than 30 μm was considered good.

Example 1
Preparation of neutralized product of alkali-soluble copolymer (A) Methyl methacrylate: 22.5 parts, methacrylic acid: 6.5 parts, sodium styrenesulfonate: 1 part, octyl thioglycolate: 2.35 parts, polyvinyl 3 parts of alcohol (polymerization degree 500, saponification degree 88 mol%, manufactured by Kuraray Co., Ltd.): 3 parts and ion-exchanged water: 30 parts were stirred and mixed to prepare a dispersion. On the other hand, 85 parts of ion-exchanged water was charged into a reactor equipped with a stirrer with nitrogen inside, and then heated to 80 ° C., and 40 parts of 5% aqueous potassium persulfate solution was added to the reactor. The monomer was polymerized by continuously adding the dispersion prepared above to the reactor maintained at 80 ° C. over 2 hours. After completing the addition of the dispersion, the mixture was further maintained at 80 ° C. for 30 minutes to obtain an aqueous dispersion of an alkali-soluble copolymer. Subsequently, 28% ammonia water was added to the obtained aqueous dispersion of the alkali-soluble copolymer so as to have an equimolar amount with methacrylic acid constituting the copolymer, and then the solid content concentration was adjusted to 25. % Neutralized aqueous solution of alkali-soluble copolymer was obtained.

Production of Latex Subsequently, the neutralized aqueous solution of the alkali-soluble copolymer obtained above was charged into a 30-part reactor in terms of solid content, then heated to 80 ° C., and 5% aqueous potassium persulfate solution: 12 .6 parts were added to the reactor. A reactor maintained at 80 ° C. was obtained by mixing methyl methacrylate: 55 parts, butyl acrylate 45 parts, and a crosslinkable monomer tetraethylene glycol dimethacrylate: 0.3 part. The monomer was polymerized by continuously adding the mixture of the monomers (B) over 2 hours. After the addition of the monomer (B) mixture was completed, the mixture was further polymerized for 3 hours, and finally cooled to 30 ° C. to obtain a latex having a solid content concentration of 35% and a pH of 7.2.
About the obtained latex, while measuring the gel content in latex by the said method, latex was formed into a film by said each method, and water resistance, adhesiveness, and glossiness were evaluated. The results are shown in Table 1.

Preparation of water-based paint containing inorganic pigment First, styrene-maleic anhydride oligomer SMA 3000 (Tg 125 ° C., acid value 285 KOH mg / g, weight average molecular weight 9,500, styrene: maleic acid = 3: 1, manufactured by Sartomer) 28 A styrene-maleic anhydride oligomer solution having a solid content concentration of 50% was prepared by complete neutralization with an aqueous ammonia solution. Next, the solution prepared above is added to the solid content of 100 parts of the latex obtained above so that the addition amount of the styrene-maleic anhydride oligomer is 1.5 parts. Got.

Next, while stirring the mixed solution, 2 parts of antifoaming agent (SM5515 manufactured by Toray Dow Corning Silicone Co., Ltd.): 240 parts of calcium carbonate and 60 parts of titanium oxide with respect to 100 parts of latex solids. Then, 10 parts of methanol and 17 parts of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (CS-12, manufactured by Chisso Corp.) were added to prepare an inorganic pigment. An aqueous paint containing was obtained. In this example, the pH of the obtained water-based paint was adjusted to 10.5 using a 28% aqueous ammonia solution.
The obtained water-based paint was evaluated for the degree of pigment dispersion, storage stability, and water resistance by the above methods. The results are shown in Table 2.

Examples 2 and 3
A latex was produced in the same manner as in Example 1 except that the ratio of each component was changed to the ratio shown in Table 1. Evaluation was performed in the same manner as in Example 1. The obtained results are shown in Table 1.

  An aqueous paint containing an inorganic pigment was prepared in the same manner as in Example 1 except that the latex obtained above was used and the ratio of each component was changed to the ratio shown in Table 2. Example 1 And evaluated. The obtained results are shown in Table 2.

  In Example 2, as the alcoholic hydroxyl group-containing water-soluble polymer compound contained in the alkali-soluble copolymer, a cationic group (quaternary ammonium salt) is used together with the polyvinyl alcohol having a polymerization degree of 500 used in Example 1. A cation-modified polyvinyl alcohol (viscosity 18.0 to 22.0 mPa · s, saponification degree 85.5 to 88.0 mol%, manufactured by Nippon Synthetic Chemical Co., Ltd.) in the side chain was used. Furthermore, in Example 2, as a styrene-maleic anhydride oligomer in preparing a water-based paint, SMA 2625 (Tg 110 ° C., acid value 220 KOH mg / g, weight average molecular weight 9,000, styrene: maleic acid = 2: 1, Sartomer) was used.

  In Example 3, polyvinyl alcohol (polymerization degree 1700, saponification degree 98 to 99.5 mol%, manufactured by Kuraray Co., Ltd.) is used as the alcoholic hydroxyl group-containing water-soluble polymer compound contained in the alkali-soluble copolymer. did. Furthermore, in Example 3, as the styrene-maleic anhydride oligomer in preparing the water-based paint, SMA2000 (Tg 135 ° C., acid value 355 KOH mg / g, weight average molecular weight 7,500, styrene: maleic acid = 2: 1, Sartomer) was used.

Comparative Examples 1-5
A latex was produced in the same manner as in Example 1 except that the ratio of each component was changed to the ratio shown in Table 1. Evaluation was performed in the same manner as in Example 1. The obtained results are shown in Table 1.

  An aqueous paint containing an inorganic pigment was prepared in the same manner as in Example 1 except that the latex obtained above was used and the ratio of each component was changed to the ratio shown in Table 2. Example 1 And evaluated. The obtained results are shown in Table 2.

  In Comparative Example 1, as the styrene-maleic anhydride oligomer in preparing the aqueous paint, SMA 1000 (Tg 155 ° C., acid value 480 KOH mg / g, weight average molecular weight 5,500, styrene: maleic acid = 1: 1, Sartomer) was used.

From Tables 1 and 2, the following can be confirmed.
That is, in Comparative Examples 1 to 5 in which the gel content in the latex particles was less than 50% by weight, the results were inferior in the following points.
In Comparative Examples 1 to 3, the adhesion to all base materials of mortar board, PVC board, PET board, ABS board and aluminum board is poor, and the glossiness is deteriorated. Even in the case of containing a water-based paint, the water resistance was inferior.
In Comparative Example 4, the adhesion to the mortar plate and the ABS plate was inferior, and even when an inorganic pigment was included to form a water-based paint, the water resistance was inferior.
In Comparative Example 5, the adhesion to the mortar plate and the ABS plate is inferior, and the glossiness is also deteriorated. The results were inferior to the degree, storage stability and water resistance.

  In Comparative Examples 1 to 3 and 5, the ratio between the alcoholic hydroxyl group-containing water-soluble polymer compound and the crosslinkable monomer tetraethylene glycol dimethacrylate was outside the preferred range of the present invention. As a result, the gel content in the latex particles was lowered. In Comparative Example 4, since the ratio of the alkali-soluble copolymer (A) and the monomer (B) was outside the preferred range of the present invention, the gel content in the latex particles was The result was lower.

  On the other hand, in Examples 1 to 3 within the predetermined range of the present invention, extremely good adhesion to all base materials of mortar plate, PVC plate, PET plate, ABS plate and aluminum plate. In addition, even when an inorganic pigment was included to form a water-based paint, good results were obtained.

Claims (6)

A latex obtained by polymerizing a monomer in the presence of a neutralized product of an alkali-soluble copolymer,
The alkali-soluble copolymer contains an alcoholic hydroxyl group-containing water-soluble polymer compound,
The latex content of the latex particles constituting the latex is 50% by weight or more with respect to 100% by weight of the whole latex particles.   The latex according to claim 1, wherein a ratio of the neutralized product of the alkali-soluble copolymer to 10 parts by weight of the monomer is 10 to 40 parts by weight.   The latex according to claim 1 or 2, wherein the monomer contains a crosslinkable monomer.   The latex according to claim 3, wherein the ratio of the water-soluble polymer compound contained in the alkali-soluble copolymer is 2 to 20 times that of the crosslinkable monomer in terms of a weight ratio.   The latex according to any one of claims 1 to 4, further comprising an inorganic pigment.   The film formed by apply | coating the latex in any one of Claims 1-5.