JPH05230433A - Adhesive for label - Google Patents

Abstract

(57) [Summary] [Structure] A label adhesive comprising a casein resin (A) and a water-insoluble, alkali-soluble or alkali-swellable substance (B). [Effect] A label adhesive having a high initial adhesiveness and having significantly improved both water-resistant adhesiveness and alkali detergency is provided.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a label adhesive. More specifically, it relates to an adhesive for bottle labels, which has good water-resistant adhesiveness in cold water and is excellent in alkali cleaning property.

[0002]

Label adhesives used in bottles, particularly bottles for filling beverages such as beer, have high adhesive strength, good water-resistant adhesive properties when immersed in cold water, and are suitable for cleaning bottles. It is necessary for the label to have a property of being peeled off from the bottle in a short time by alkaline water (hereinafter, abbreviated as "alkaline detergency").

Conventionally, starch-based adhesives, casein-based adhesives, polyvinyl alcohol-based adhesives and the like are known as such adhesives. Many proposals have been made in the past for polyvinyl alcohol-based adhesives, but the present situation is that the performance is not sufficient as an adhesive for labels that requires both the water-resistant adhesive property and the alkaline cleaning property at the same time. .. Starch-based adhesives are used as label adhesives for beer bottles because they are inexpensive and have good workability for laminating, but they lack water-resistant adhesiveness, especially aluminum vapor-deposited paper and coated paper. When used as a label, there was a problem that water resistance was not exhibited at all. Furthermore, in the past, it was pasted at a speed of about 300 to 500 pieces per minute, but recently, it has become common to stick at a speed of 700 to 1000 pieces per minute, and as a result, adhesives for labels are used. Requires excellent initial adhesion and workability.
In such a situation, the starch-based adhesive is insufficient in the initial adhesiveness, and the present situation is that the casein-based adhesive is gradually being used.

[0004]

The casein-based adhesive is a relatively well-balanced adhesive having excellent initial adhesiveness, water-resistant adhesiveness and alkali-cleaning property, but it has considerable water-resistant adhesiveness. There's a problem. In particular, if it is soaked in cold water for a long time or left in the refrigerator for a long time and left in the open air for a long time, the adhesive strength is greatly reduced, and the label easily peels off when it is lightly rubbed or when the water is wiped off with a cloth.
However, there is a contradictory relationship that if the water-resistant adhesiveness is to be improved, the alkali cleaning property is deteriorated. An object of the present invention is to provide a label adhesive which has further improved water-resistant adhesiveness, which has been a drawback of conventional casein-based adhesives, and further improved alkaline detergency.

[0005]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors to solve the above problems, a label comprising a casein resin (A) and a water-insoluble and alkali-soluble or alkali-swellable substance (B) The present invention has been accomplished by finding an adhesive for use in the present invention. The present invention will be described in detail below.

Casein resin (A) used in the present invention
Is not particularly limited, and specific examples thereof include commonly used acid casein, rennet casein, lactic casein, and modified compounds thereof.
By adopting the following formulation in the adhesive of the present invention, the water resistance can be further improved. That is, when the casein-based resin (A) is dissolved, an alkaline substance such as calcium hydroxide, calcium oxide, sodium hydroxide, sodium carbonate, sodium fluoride, water glass, or ammonia is used. A method of increasing the amount of addition and decreasing the ratio of the amount of sodium compounds to increase the ratio of ammonia; a method of reducing the total amount of alkaline substances added; adding water resistance improvers such as copper chloride, copper sulfate and zinc sulfate It is possible to adopt a prescription such as a method of doing. The solid content concentration of the aqueous solution of the casein resin (A) to be used is not particularly limited, but is preferably 20 to 60% by weight, more preferably 30 to 50% by weight. The viscosity of the casein resin (A) aqueous solution is important for developing the initial adhesiveness, and is 10 to 10 in terms of B-type viscosity at 20 ° C.
10,000 centipoise is preferable and 20,000 to 7
More preferably 10,000 centipoise.

The water-insoluble and alkali-soluble or alkali-swellable substance (B) used in the present invention is present in the form of particles in the aqueous adhesive solution because it is water-insoluble, but it is immersed in alkaline water. When it does, it must dissolve or swell. The shape of the substance (B) is not particularly limited as long as it does not impair the function of the adhesive as long as it is insoluble in water and can exist in the form of particles in the adhesive. Aqueous dispersions such as turbid dispersions are preferred, and powders are more preferred. The particle size is not particularly limited, but in the case of powder, the average particle size is preferably 100 μm or less. Specific examples of the substance (B) include a copolymer of an olefinic monomer containing a carboxyl group or an acid anhydride group, an acid-type superabsorbent resin,
Cellulosic compounds, aluminum, silica and the like can be mentioned.

As the copolymer of the olefinic monomer containing a carboxyl group or an acid anhydride group, there are olefinic monomers containing a carboxyl group or an acid anhydride group such as (meth) acrylic acid, crotonic acid, maleic anhydride, and itaconic acid. Monomers (hereinafter abbreviated as “monomer (1)”) and olefinic monomers such as α-olefins, vinyl esters, vinyl ethers, (meth) acrylic acid esters, vinyl chloride, and acrylonitrile (hereinafter referred to as “monomer”) A copolymer with the body (2) is mentioned. Carbon number as α-olefin
2 to 20 α-olefins, specifically, ethylene, propylene, butene-1, butene-2, isobutene, 2-methyl-butene-1,3-methyl-butene-
1, pentene-1, 4-methyl-pentene-1, 4-methyl-pentene-1, octene-1, diisobutylene,
Examples thereof include styrene and α-methylstyrene. Vinyl acetate as vinyl ester. Vinyl propionate, t-
Examples thereof include butyl vinyl ester and vinyl versatate. As (meth) acrylic acid ester, (meth)
Examples thereof include methyl, ethyl, butyl, 2-ethylhexyl, and lauryl ester of acrylic acid. These monomer (1) and monomer (2) can be used alone or in combination of two or more kinds. The copolymerization ratio of the monomer (1) and the monomer (2) is not particularly limited as long as it is water-insoluble and alkali-soluble or alkali-swellable, but the monomer (1) is maleic anhydride. If it is a monomer (2)
The molar ratio of / monomer (1) is preferably 0.5 / 1 to 5/1, more preferably 1/1. When the monomer (1) is (meth) acrylic acid, crotonic acid or itaconic acid, the molar ratio of monomer (2) / monomer (1) is 5 /
1 to 50/1 is preferable. Among the above copolymers, a copolymer of a carboxyl group- or acid anhydride group-containing monomer and a vinyl ester, and an α-olefin-maleic anhydride copolymer are preferable for the purpose of the present invention. However, the isobutene-maleic anhydride copolymer and the styrene-maleic anhydride copolymer are particularly preferable from the viewpoint of being water-insoluble and soluble in alkali or swelling with alkali. The above maleic anhydride may be used as a mixture with maleic acid, a maleic acid salt, a maleic acid monoester or the like.

As the acid type superabsorbent resin, a superabsorbent resin subjected to dealkalization treatment (for example, washing treatment with acid), (meth) acrylic acid salt or (meth) acrylic acid is used in combination with a crosslinking agent. Examples of the highly water-absorbent resin produced by These are present in the form of powder with almost no dissolution or swelling in ordinary water, but largely swell in an alkaline aqueous solution. Specific examples of the super absorbent polymer include cross-linked products of polyacrylic acid salts, cross-linked products of α-olefin-maleic anhydride copolymer salts, cross-linked products of acrylic acid / starch graft polymers, and starch-acrylonitrile graft copolymers. Examples include hydrolyzed products of polymers.

As the cellulosic compound, acid type carboxymethyl cellulose (hereinafter abbreviated as CMC),
Examples thereof include metal salts of CMC having a relatively low degree of substitution with carboxylic acid, hydroxypropylmethyl cellulose and derivatives thereof, and it is preferable to use them as fine powders. Among them, acid type CMC is preferable. The substance (B) in the present invention is water-insoluble and has a property of dissolving or swelling in an alkaline aqueous solution. As alkali, hydroxides and carbonates of sodium, potassium, lithium, etc .;
Examples include ammonia, amines, hydroxides and carbonates of alkaline earth metals, etc., but sodium hydroxide is used as an alkaline aqueous solution in the beer industry, and it is practical and useful if the above effects can be exhibited in this aqueous solution. Is.

Among the above-mentioned water-insoluble and alkali-soluble or alkali-swellable substances (B), α-olefin-maleic anhydride copolymer, crotonic acid-modified polyvinyl acetate and metallic aluminum powder are preferable, and further water resistant. The isobutylene-maleic anhydride copolymer and the styrene-maleic anhydride copolymer are particularly preferred from the viewpoints of properties and alkali detergency. These are preferably used in the form of fine powder.

The mixing weight ratio (solid content ratio) of the casein-based resin (A) and the water-insoluble and alkali-soluble or alkali-swellable substance (B) is not particularly limited, but the adhesiveness and the alkali-cleaning property are not limited. From the point, casein resin (A) 1
2 to 500 parts by weight of the substance (B) is preferable, and 20 to 300 parts by weight is more preferable, relative to 00 parts by weight. If the substance (B) is less than 2 parts by weight, the effect of improving the alkali detergency is small, and if the substance (B) is more than 500 parts by weight, the water-resistant adhesive strength and the initial adhesive strength are lowered, and the function as an adhesive tends to be lowered. There is.

In the adhesive for labels of the present invention, the casein resin and the substance (B) are essential components, but a filler may be used together if necessary for improving fluidity and improving initial tack. .. Further, an aqueous emulsion, a thickener, an antifoaming agent, an antiseptic agent, an antifungal agent, a viscosity stabilizer, a coloring agent, a deodorant, a fragrance and the like can be appropriately added. However, if the amount of these additives added is unnecessarily large, the high-speed coating property and the like will be adversely affected, so caution is required.

The method for producing the label adhesive of the present invention is not particularly limited, and a fine powder of the water-insoluble, alkali-soluble or alkali-swellable substance (B) is mixed with the aqueous solution of the casein resin (A). It can be manufactured. The prepared adhesive for labels of the present invention is used for labels, and among them, it is suitable for labels for glass bottles for beverages, particularly labels for beer bottles. The solid content concentration of the adhesive for labels of the present invention is preferably 20 to 60% by weight, more preferably 30 to 50% by weight. Although the viscosity of the adhesive varies depending on each application, when high-speed coating property is intended, the viscosity at the bonding temperature is 5,000 B-type viscosity.
0-100,000 centipoise is preferred, and 10.0
More preferably, it is from 00 to 50,000 centipoise.

Labels for which the adhesive for labels of the present invention is used are paper, processed paper (paper that has been subjected to aluminum vapor deposition processing, aluminum lamination processing, varnish processing, resin processing, etc.), paper such as synthetic paper, and organic compounds. Labels made from inorganic compound films, metal films, etc. are targeted. The other adherend may be of any type, and examples thereof include inorganic substances such as glass, metal, and plastics, and organic substances. Among them, glass bottles for beverages are preferable.

[0016]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In the examples, "%" and "parts" are based on weight unless otherwise specified.

Example 1 100 parts of casein, 20 parts of calcium hydroxide, 0.25 parts of sodium hydroxide, 0.25 parts of sodium fluoride, 16 parts of 25% ammonia water, 3 parts of zinc sulfate, 0.8 parts of copper sulfate, 180 parts of water are usually used. A casein aqueous solution was prepared by mixing and dissolving according to the method. Solids concentration 42.5%, B type viscosity at 20 ℃ is 46,0
It was 00 centipoise. Next, 4 parts of fine powder having an average particle size of 50 μm obtained by pulverizing a styrene-maleic anhydride copolymer (manufactured by Arco Co .; SMA-1000) was added to 100 parts of the above casein aqueous solution and mixed sufficiently. , An adhesive of the present invention was prepared. The obtained adhesive was a mixture in which a styrene-maleic anhydride copolymer was dispersed as a fine powder in an aqueous casein solution, and had good fluidity. The adhesive of the present invention has a solid content of 44.3% and a viscosity at 20 ° C.
It was 48,000 centipoise. As an adhesion test, a glass plate that had been washed and dried in advance was preheated to 40 ° C., and the adhesive was applied to the label paper using a bar coater to obtain a solid content of 10 g /
It was applied so that m ↑ 2, immediately adhered to a glass plate, and then lightly pressed with a rubber roller to prepare a test piece.
After 30 seconds, a 180-degree peel test was performed using an autograph to measure the initial adhesive force. Also, attach the bonded test piece to 20
After standing at 65 ° C. and 65% RH for 3 days, the normal adhesive strength was measured by the same method as the measurement of the initial adhesive strength. As a cold water adhesion test, soak the above test piece in cold water at 10 ° C, take out the test piece from the cold water after 20 days, put a nail between the glass plate surface and the label paper, and peel off the adhesiveness. It was judged. As an alkali detergency test, the test piece (dried at 40 ° C. for 48 hours) was immersed in a 4% aqueous sodium hydroxide solution at 70 ° C. so that the adhesive surface was vertical and left for 30 minutes. Measure the time until spontaneous peeling,
The alkali detergency was evaluated. The results are shown in Table 1.

Example 2 To 100 parts of the casein solution prepared in Example 1 was added 5 parts of an isobutylene-maleic anhydride copolymer (Kuraray's Isoban-04) fine powder (average particle size 18 μm). The adhesive of the present invention was prepared by dispersing them. The resulting adhesive has a solids concentration of 45.2% and a viscosity at 20 ° C of 4
It was 8,500 centipoise. In the same manner as in Example 1, the adhesiveness and the alkali detergency were measured. The results are shown in Table 1.
Shown in.

Example 3 100 parts of the casein solution prepared in Example 1 was added to an alkali-soluble polyvinyl acetate emulsion (PVAcEm,
Polymer acid value 48, solid content concentration 45%) 10 parts,
Mix evenly. The emulsion particles were not dissolved at all in the adhesive, were uniformly dispersed in the emulsion state, and had excellent fluidity. The solid content of the obtained adhesive was 42.7%, and the viscosity at 20 ° C was 41,500 centipoise. In the same manner as in Example 1, the adhesiveness and the alkali cleaning property were measured. The results are shown in Table 1.

Comparative Example 1 Adhesiveness and alkali detergency were measured in the same manner as in Example 1 except that the casein aqueous solution prepared in Example 1 was used alone as an adhesive. The results are shown in Table 1.

Comparative Example 2 Using a casein-based adhesive (adhesive not containing the substance (B) of the present invention) of a commercially available label for beer bottles, the adhesive property and the alkaline cleaning property were the same as in Example 1. It was measured. The results are shown in Table 1.

[0022]

[Table 1]

(Explanation of Symbols) O: Good Δ: Almost good XX: Very poor (* 1): Peeling after immersion for 20 seconds. (* 2): Peeling after immersion for 32 seconds. (* 3): Peeling after immersion for 68 seconds. (* 4): No peeling occurred even after immersion for 30 minutes. (* 5): Peeled easily when touched by hand after immersion for 10 days, and spontaneously peeled after immersion for 10 days.

[0024]

EFFECTS OF THE INVENTION The present invention provides an adhesive which has further improved water-resistant adhesiveness, which has been a drawback of conventional casein-based adhesives, and further improved alkaline detergency. Casein-based adhesives have excellent initial adhesive strength that is suitable for high-speed coating, but they have problems with cold water resistance, and label peeling may occur when the user dips the bottle in cold water to cool it. It was happening. It is impossible to improve both of these properties at once because there is a contradictory relationship that the alkali releasability deteriorates when trying to improve the water resistance. On the other hand, the label adhesive of the present invention comprising the casein-based resin (A) and the water-insoluble and alkali-soluble or alkali-swellable substance (B) has high initial adhesiveness and further has the above-mentioned water-resistant adhesion. It has an extremely high industrial value in that it has significantly improved both the cleaning property and the alkaline cleaning property.

Claims (1)

[Claims] 1. A casein resin (A) and a water-insoluble and alkali-soluble or alkali-swellable substance (B)
Label adhesive consisting of.