JP5399607B2 - Non-adhesive water-based undercoat material for leather - Google Patents

Description

  The present invention relates to a non-adhesive water-based undercoat material for leather that has excellent cold-bending resistance and good mold effectiveness and releasability when embossed.

  Conventionally, various water-based resins, mainly acrylic emulsions, have been used as an undercoat material for leather. However, when trying to obtain flexibility, adhesion occurs when embossing and the undercoat is peeled off or peeled off from the mold. There were problems such as difficulty. In addition, when a resin having a high glass transition temperature (hereinafter referred to as Tg) is used to prevent adhesion at the time of embossing, there is a problem in cold bending resistance. In order to solve these problems, attempts have been made to make improvements by grafting or crosslinking.

  As a grafting method, a copolymer obtained by grafting methyl methacrylate and a fluorine-containing acrylic ester to an acrylate ester (for example, see Patent Document 1) is known. However, in Patent Document 1, mechanical stability and water resistance are known. It is intended for fastness and good touch by using an acrylic acid dispersion having good solvent resistance, and does not take into account flexibility at low temperatures and does not describe low-temperature flexibility.

  On the other hand, as a method by crosslinking, a method of crosslinking a sulfonic acid or phosphoric acid-containing acrylic resin with carbodiimide is known (for example, see Patent Document 2), but the purpose is to improve non-yellowing, solvent resistance, and scratch resistance. The flexibility is not considered at all.

  Further, a leather coating material comprising an emulsion in which an acetoacetate or acetoacetamide-containing monomer is an essential crosslinking component and further has a carboxyl group metal-crosslinked is known (for example, see Patent Document 3). Although it has been described that the embossing property and wet flexibility are excellent, flexibility at low temperatures such as cold bending resistance is not considered at all.

JP-A-8-048732 JP-A-9-188823 JP 2000-239604 A

  The present invention provides an undercoat material for leather that solves the above-mentioned problems, has excellent cold-bending resistance, has a good mold effect during embossing, has little adhesion during embossing, and has good releasability. For the purpose.

That is, in the present invention, an acrylic resin having a Tg of −30 ° C. or lower as a main skeleton, a monomer that forms a vinyl polymer having a Tg of 60 ° C. or higher, and a monomer having a carboxyl group are used as the acrylic resin. A resin obtained by grafting 1 to 30 parts by weight of the monomer forming the vinyl polymer and 0.1 to 10 parts by weight of the monomer having a carboxyl group with respect to 100 parts by weight of the acrylic resin. The present invention relates to a non-adhesive water-based undercoat material for leather, which contains an acrylic emulsion and a metal crosslinking agent capable of crosslinking reaction with the carboxyl group.

  The non-adhesive water-based undercoat material for leather of the present invention grafts a monomer having a carboxyl group with a monomer that forms a vinyl polymer having a high Tg and has a low Tg and a flexible acrylic main chain. By forming it into a metal cross-link, it is possible to form a film having excellent cold-bending resistance, good mold effectiveness at the time of stamping, little adhesion at the time of stamping, and good releasability.

In the present invention, the acrylic resin having a Tg of −30 ° C. or less as a main skeleton, a monomer that forms a vinyl polymer having a Tg of 60 ° C. or more, and a monomer having a carboxyl group are added to the acrylic resin . An acrylic resin containing 1 to 30 parts by weight of a monomer forming the vinyl polymer and 0.1 to 10 parts by weight of a monomer having a carboxyl group grafted to 100 parts by weight of an acrylic resin The present invention relates to a non-adhesive aqueous undercoat material for leather containing an emulsion and a metal crosslinking agent capable of crosslinking reaction with the carboxyl group.

  The non-adhesive water-based undercoat material for leather of the present invention has a low Tg of -30 ° C. or less for the acrylic resin main chain forming the main skeleton, and therefore can form a flexible and excellent cold-flexible film.

  The Tg of the acrylic resin constituting the main skeleton is −30 ° C. or lower, preferably −35 ° C. or lower, and the lower limit is not particularly limited, but is preferably −60 ° C. or higher, and is −55 ° C. or higher. It is more preferable. When Tg exceeds −30 ° C., flexibility tends to decrease and cold bending resistance tends to decrease, and when it is lower than −60 ° C., it tends to be difficult to suppress tackiness.

In the present invention, the flexible acrylic resin includes a monomer that forms a vinyl polymer (hard resin) having a high Tg of 60 ° C. or higher and a water resistance and a monomer having a carboxyl group. By cross-linking the resin obtained by graft polymerization, it is tough and excellent in flexibility, has good mold effectiveness when pressed, has little adhesion during pressing, and has excellent cold bending resistance. A film can be formed.

The Tg of the vinyl polymer is more preferably 60 ° C. or higher. Although an upper limit is not specifically limited, It is preferable that it is 150 degrees C or less, and it is more preferable that it is 120 degrees C or less. If the Tg is less than 20 ° C., it tends to be difficult to suppress the adhesiveness of the coating surface, which causes the peeling of the coating film during mold pressing and the deterioration of the release property. On the other hand, when Tg exceeds 150 ° C., the film forming property is lowered, and it tends to be difficult to form a uniform coating film.

  The non-adhesive water-based undercoat material for leather of the present invention is obtained by first polymerizing a monomer that forms a flexible acrylic resin in an aqueous medium, and then an appropriate amount of a hard resin according to the composition of the flexible acrylic resin. And a monomer having a carboxyl group can be graft-polymerized on the acrylic resin and further crosslinked by metal crosslinking.

  The flexible acrylic resin is mainly composed of at least one alkyl (meth) acrylate or alkoxy acrylate. Here, the main component is that the alkyl (meth) acrylate or alkoxy acrylate is 60% by weight or more, preferably 70% by weight or more in the flexible acrylic resin. When the alkyl (meth) acrylate or alkoxy acrylate is less than 60% by weight, the flexibility of the film tends to be lowered, and the cold bending resistance tends to be lowered.

  Examples of the alkyl (meth) acrylate include n-butyl acrylate, i-butyl acrylate, 2-ethylhexyl (meth) acrylate, isomyristyl acrylate, and lauryl (meth) acrylate. Examples of the alkoxy acrylate include , Methoxyethyl acrylate, ethoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, and the like. Among these, alkyl (meth) acrylate is preferable from the viewpoint of reactivity, storage stability, weather resistance, and the like.

  In addition to the alkyl (meth) acrylate or alkoxy acrylate, examples of the monomer that forms the flexible acrylic resin include hydroxypropyl acrylate, hydroxyhexyl acrylate, butylaminoethyl acrylate, and dibutylaminoethyl acrylate. .

  Examples of the grafting agent include unsaturated group-containing (meth) acrylates such as dicyclopentenyl acrylate and cyclopentenyloxyethyl (meth) acrylate. Among these, cyclopentenyloxyethyl acrylate is preferable from the viewpoint of reactivity and graft ratio.

  The content of the grafting agent is preferably 0.5 to 10 parts by weight and more preferably 1 to 8 parts by weight with respect to 100 parts by weight of the flexible acrylic resin. If the grafting agent is less than 0.5 parts by weight relative to the flexible acrylic resin, the graft point tends to be too small and the tackiness tends not to disappear, and if it exceeds 10 parts by weight, the physical properties of the film tend to decrease. .

Flexibility acrylic resin and graft polymerization, as a monomer forming a hard resin, styrene, alpha-methyl styrene, methyl methacrylate, t - butyl methacrylate, etc. acrylonitrile may be mentioned. Among these, methyl methacrylate is preferable from the viewpoint of water resistance, weather resistance, heat discoloration, and the like.

  The content of the hard resin is not particularly limited and can be appropriately selected depending on the composition of the flexible resin and the hard resin to be combined, but is preferably 1 to 30% by weight with respect to the flexible acrylic resin. 3 to 20% by weight is more preferable. If the content of the hard resin is less than 1% by weight, the surface tackiness tends to remain, and if it exceeds 30% by weight, the flexibility tends to decrease and the cold-bending resistance after top coating tends to deteriorate.

  Examples of the monomer having a carboxyl group include acrylic acid, methacrylic acid, crotonic acid, maleic acid and anhydrides thereof, dicarboxylic acids such as fumaric acid and itaconic acid, and monoalkyl esters thereof. Among these, acrylic acid is preferable from the viewpoints of reactivity and heat discoloration.

  The content of the monomer having a carboxyl group is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 7 parts by weight with respect to 100 parts by weight of the flexible resin. If the content of the monomer having a carboxyl group is less than 0.1 parts by weight, the effect of metal crosslinking tends to be small and stickiness tends to remain, and if it exceeds 10 parts by weight, storage stability tends to cause problems. is there.

  As the emulsion polymerization method, a general persulfate, hydrogen peroxide, water-soluble azo compound, etc. can be used, and the reaction can be performed at a high temperature of 70 ° C. or more. However, in terms of film properties, film weather resistance, etc. The reaction is preferably carried out at 50 ° C. or lower using an oxidation-reduction system in which a general persulfate, hydrogen peroxide and the like are combined with an appropriate reducing agent such as ascorbic acid or sodium bisulfite. The amount of these oxidizing agent and reducing agent used is preferably 0.01 to 2.0 parts by weight per 100 parts by weight of the emulsion.

  In the polymerization, it is preferable to use a surfactant. Examples of the surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene styrenated phenyl ethers, polyoxyethylene polyoxypropylene block polymers, and the like, which are general nonionic activators. Also, an alkyl sulfate salt, polyoxyethylene alkyl ether sulfate salt, alkylbenzene sulfonate, etc., which are anionic activators, can be used at the same time. The amount of the surfactant used is preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the emulsion.

  The water content of the acrylic emulsion containing the resin is preferably 40 to 80% by weight, more preferably 45 to 75% by weight of the entire acrylic emulsion. If the amount is less than 40% by weight, the viscosity of the emulsion tends to be high and storage stability tends to be problematic. On the other hand, if it exceeds 80% by weight, the transportation cost becomes a problem and the coating workability decreases.

  Examples of the metal crosslinking agent include divalent or higher polyvalent metal compounds such as salts, complexes, oxides, and hydroxides of divalent or higher polyvalent metals. Examples of the divalent or higher polyvalent metal include magnesium, calcium, iron, zinc, barium, aluminum, and zirconium. Examples of the anion for forming a salt include carbonate ion, bicarbonate ion, acetate ion, Examples thereof include phosphate ion, tartrate ion, sulfate ion and the like. Examples of the ligand that forms a complex of a polyvalent metal include glycine, alanine, ammonia, ethylenediamine, triethanolamine, and the like in addition to the above anions.

  Specifically, zinc acetate as a salt of a polyvalent metal, zinc carbonate ammonia, zinc acetate ammonia, zinc phosphate ammonia or the like as a complex of a polyvalent metal can be used.

  The amount of the metal crosslinking agent used is preferably 0.1 to 1 equivalent, more preferably 0.2 to 0.9 equivalent per 1 equivalent of the carboxyl group. Moreover, it is preferable that the usage-amount of a metal crosslinking agent is 0.1-10 weight part with respect to 100 weight part of flexible acrylic resins.

  In addition to the acrylic resin grafted with the vinyl polymer, water, an antifoaming agent, a thickener, a leveling agent, and the like can be added to the non-adhesive aqueous undercoat material for leather of the present invention. Further, it can be used in combination with a resin having other characteristics, a urethane resin, an acrylic resin, or the like depending on the application.

  The Tg of the non-adhesive aqueous undercoat material for leather of the present invention is preferably −25 to −55 ° C., more preferably −30 to −50 ° C. When Tg is less than −55 ° C., it tends to be difficult to suppress the tackiness, and when it exceeds −25 ° C., flexibility tends to be lowered and cold bending resistance tends to be deteriorated.

  The non-adhesive water-based undercoat material for leather of the present invention has excellent embossability and excellent cold-bending resistance, and therefore is suitably used for leather that requires flexibility at low temperatures such as automobiles. It is something that can be done. Examples of automobile leather include car seats and handle covers.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, it is not limited to these Examples. Unless otherwise specified, “part” means part by weight, and “%” means% by weight.

  The undercoat materials obtained in Examples and Comparative Examples were evaluated by the following methods.

<Composition of aqueous undercoat preparation liquid>
Using the undercoat materials obtained in Examples and Comparative Examples, an aqueous primer coating solution was prepared according to the following formulation.
Disper Color Black EX (manufactured by Toupe Co., Ltd.) 100 parts Water 150 parts Undercoat material obtained in Examples and Comparative Examples 200 parts

<Composition of lacquer topcoat preparation liquid>
A lacquer topcoat preparation solution was prepared according to the following composition.
Lacquer # 140 Clear (made by Tope Corp.) 100 parts Lacquer thinner # 2000 (made by Tope Corp.) 250 parts Lacquer NB Thinner M (made by Tope Corp.) 50 parts

<Pigment miscibility>
The aqueous undercoat preparation liquid prepared according to the above specifications was cast on a glass plate, visually checked for irregularities and the like, and evaluated according to the following evaluation criteria.
○ ・ ・ ・ No abnormality × ・ ・ ・ There are aggregates

<Iron separation>
The aqueous primer coating solution was applied to silver slick leather by spraying twice, dried, ironed at 80 ° C. × 20 Kg / cm ² , the degree of separation of the coated leather was confirmed, and evaluated according to the following evaluation criteria.
○ ・ ・ ・ Painted leather can be peeled off without resistance.

<Adhesiveness of coating film>
After ironing, the aqueous primer coating solution was further applied by spraying twice, and after drying, the degree of adhesion was confirmed by finger touch and evaluated according to the following evaluation criteria.
○ ・ ・ ・ Adhesion is not felt Δ ・ ・ ・ Somewhat stickiness is felt × ・ ・ ・ Adhesion is felt

<Effect of mold>
The effect of the mold when die-pressing was performed on the coated leather evaluated for tackiness at 90 ° C. × 200 Kg, and the piece was evaluated according to the following evaluation criteria.
○ ・ ・ ・ No die cut and uneven surface clearly △ ・ ・ ・ Rounded convex part and lack of sharpness × ...

<Cold bending resistance>
The coated leather dried by applying the aqueous undercoat preparation liquid to silver slick by spraying twice was applied to a flexometer under the condition of −15 ° C. until cracking occurred, and evaluated according to the following evaluation criteria.
1 ... No cracks occurred even after 100,000 times 2 ... Cracks occurred after 50,000 times and less than 100,000 times 3 ... Cracks occurred after 10,000 times and less than 50,000 times ..Crack occurred after less than 10,000 times

<Tensile strength, elongation>
The sample is poured into a mold, a film having a thickness of about 80 to 90 μm is produced, and the die-cut test piece is pulled with a universal tension / compression tester (manufactured by Toyo Seiki Co., Ltd.) at a pulling speed of 200 mm / min. Strength and elongation were measured. (Measurement temperature 23 ° C, humidity 50%)

Example 1
After dissolving 10 parts Neugen TDS-500F (Daiichi Kogyo Seiyaku Co., Ltd.) and 10 parts Lebenol WZ (Kao Co., Ltd.) in 190 parts of ion-exchanged water in a 1 L beaker, 280 parts of butyl acrylate (BA), 15 parts of methyl methacrylate (MMA), 10 parts of cyclopentenyloxyethyl acrylate (CPOEA) and 7.5 parts of acrylic acid (AA) were added. Further, 0.5 part of sodium bisulfite was dissolved in 10 parts of ion-exchanged water and added, and then applied to a homomixer to obtain a monomer emulsion.

  In a 1 L flask equipped with a stirrer, temperature sensor, and reflux condenser, 250 parts of ion-exchanged water was added and adjusted to 20 ° C. in a nitrogen atmosphere. Then, 10% of the emulsion, 1 part of ammonium persulfate, 1 part of ferrous sulfate .01 parts were added to initiate the reaction. In addition, 50 parts of ion-exchanged water was used for washing the container in which the emulsion was weighed, dissolving ammonium persulfate and ferrous sulfate, and washing the container. Thereafter, the temperature was adjusted to 30 ° C., and the remaining emulsion was added dropwise over 120 minutes. The Tg of the acrylic resin obtained here was -44 ° C.

  After completion of dropping, the temperature is maintained at 30 ° C. for 30 minutes, and then the temperature is raised to 40 ° C., 0.2 part of ammonium persulfate and 0.1 part of sodium hydrogen sulfite are dissolved in 10 parts of ion-exchanged water, and 10 parts of methyl methacrylate are added. The reaction was carried out while dropping 10 parts of acrylic acid over 20 minutes. Thereafter, the temperature was kept at 40 ° C. for 60 minutes to terminate the reaction. After cooling, pH adjustment was performed with 10 parts of 28% ammonia water and 35.7 parts of ion-exchanged water to obtain a graft copolymer.

  Thereafter, 100 parts of a 20% zinc acetate solution was added to obtain an undercoat material. The undercoat material had a Tg of −39 ° C., and the amount of zinc acetate added was 0.75 equivalent to the carboxyl group.

  The evaluation results are shown in Table 3.

Examples 2-3
Polymerization was carried out in the same manner as in Example 1 except that the monomer composition in the monomer emulsion, the composition of the monomer to be grafted, and the amount of zinc acetate added were as shown in Table 1.

  The evaluation results are shown in Table 3.

Comparative Example 1
In a 1 L beaker, 10 parts Neugen TDS-500 and 10 parts Lebenol WZ were dissolved in 190 parts ion-exchanged water, followed by 280 parts butyl acrylate, 5 parts methyl methacrylate, 10 parts cyclopentenyloxyethyl acrylate, and 17.5 parts acrylic acid. Added. Further, 0.5 part of sodium bisulfite was dissolved in 10 parts of ion-exchanged water and added, and then applied to a homomixer to obtain a monomer emulsion.

  In a 1 L flask equipped with a stirrer, a temperature sensor, and a reflux condenser, 350 parts of ion-exchanged water was added, adjusted to 20 ° C. in a nitrogen atmosphere, and then 10% of the above emulsion, 1 part of ammonium persulfate, 1 part of ferrous sulfate. 01 parts were added to initiate the reaction. In addition, 50 parts of ion-exchanged water was used for washing the container in which the emulsion was weighed, dissolving ammonium persulfate and ferrous sulfate, and washing the container. Thereafter, the temperature was adjusted to 30 ° C., and the remaining emulsion was added dropwise over 120 minutes. The Tg of the acrylic resin obtained here was -44 ° C.

  Hold at 30 ° C. for 30 minutes after the end of dropping. Thereafter, the temperature was raised to 40 ° C., 0.2 part of ammonium persulfate and 0.1 part of sodium hydrogen sulfite were dissolved in 10 parts of ion-exchanged water and added, and the reaction was carried out while dropping 20 parts of methyl methacrylate over 20 minutes. Thereafter, the reaction was terminated by maintaining the temperature at 40 ° C. for 60 minutes. After cooling, the pH was adjusted with 10 parts of 28% ammonia water and 25.7 parts of ion-exchanged water to obtain a graft copolymer. The undercoat material had a Tg of -39 ° C.

  The evaluation results are shown in Table 3.

Comparative Example 2
In a 1 L beaker, 10 parts Neugen TDS-500 and 10 parts Lebenol WZ were dissolved in 190 parts ion-exchanged water, then 285 parts butyl acrylate, 25 parts methyl methacrylate, 10 parts cyclopentenyloxyethyl acrylate, and 17.5 parts acrylic acid. Added. Further, 0.5 part of sodium bisulfite was dissolved in 10 parts of ion-exchanged water and added, and then applied to a homomixer to obtain a monomer emulsion.

  In a 1 L flask equipped with a stirrer, a temperature sensor, and a reflux condenser, 250 parts of ion-exchanged water was added, adjusted to 20 ° C. in a nitrogen atmosphere, and then 10% of the emulsion, 1 part of ammonium persulfate, 1 part of ferrous sulfate 01 parts were added to initiate the reaction. In addition, 50 parts of ion-exchanged water was used for washing the container in which the emulsion was weighed, dissolving ammonium persulfate and ferrous sulfate, and washing the container. Thereafter, the temperature was adjusted to 30 ° C., and the remaining emulsion was added dropwise over 150 minutes.

  After completion of the dropwise addition, the reaction was terminated by maintaining at 30 ° C. for 60 minutes, and after cooling, pH was adjusted with 10 parts of 28% ammonia water and 31 parts of ion-exchanged water to obtain a random copolymer. Thereafter, 100 parts of a 20% zinc acetate solution was added to obtain an undercoat material. The undercoat material had a Tg of −39 ° C., and the amount of zinc acetate added was 0.75 equivalent to the carboxyl group.

  The evaluation results are shown in Table 3.

Comparative Example 3
Polymerization was carried out in the same manner as in Example 1 except that the monomer composition in the monomer emulsion, the composition of the monomer to be grafted, and the amount of zinc acetate added were as shown in Table 2.

  The evaluation results are shown in Table 3.

  As is clear from this result, the emulsion grafted with a monomer having a carboxyl group had excellent embossing properties and cold bending resistance compared to an emulsion not using a monomer having a carboxyl group.

Claims (1)

An acrylic resin having a glass transition temperature of −30 ° C. or lower as a main skeleton, a monomer that forms a vinyl polymer having a glass transition temperature of 60 ° C. or higher, and a monomer having a carboxyl group are added to the acrylic resin . An acrylic resin containing 1 to 30 parts by weight of a monomer forming the vinyl polymer and 0.1 to 10 parts by weight of a monomer having a carboxyl group grafted to 100 parts by weight of an acrylic resin A non-adhesive aqueous undercoat material for leather comprising an emulsion and a metal crosslinking agent capable of crosslinking reaction with the carboxyl group.