JP2002138266A - Cold seal adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cold seal adhesive having a high overall performance such as the relaxation of deterioration of the cold seal bonding strength by heat, light, oxygen, ozone, or the like, and good blocking resistance, high cold seal bonding strength and good printing aptitude. SOLUTION: This cold seal adhesive comprises 20-70 wt.% of a modified natural gum latex obtained by graft polymerization of an acrylate compound with a natural gum latex. Preferably, the modified natural gum latex is obtained by graft polymerization of 0.1-20 pts.wt. of an acrylate compound per 100 pts.wt. of the natural gum latex. Further preferably, the modified natural gum latex is not more than 20 times for a swelling rate of a film formed therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a
An adhesive that does not cause a tack on the coated surface where the adhesive is applied to the base sheet and the adhesive layer is formed, and the other surface where the adhesive is applied and the adhesive layer is formed Even if the coated surfaces are overlapped so that the two adhesive layers are in contact with each other, the adhesive does not cause adhesion and blocking. The present invention relates to a cold seal adhesive capable of bonding surfaces.

[0002] Further, the present invention relates to an adhesion site where such a cold seal adhesive is applied to form an adhesive layer.
In particular, regarding an information carrier having such an adhesion site, various information such as information requiring confidentiality, confidentiality or concealment, or necessarily confidentiality is required for a continuous or single-sheet base sheet. The present invention relates to an information carrier in which information that is not printed is printed and is in the form of a postcard, an envelope, a business form, a delivery slip, a communication card, a folding card, a superposition sheet, an information hiding sheet, or the like.

[0003]

2. Description of the Related Art In recent years, various types of information, for example, information requiring confidentiality, confidentiality or concealment such as personal information, or advertisements, advertisements, etc. are not necessarily provided on a continuous or single-sheet base sheet. Information that does not require confidentiality is printed,
2. Description of the Related Art Information carriers in the form of postcards, envelopes, delivery slips, communication cards, folding cards, overlapping sheets, information hiding sheets, and the like are becoming widespread. In the present specification, the “substrate sheet” refers to a sheet-shaped substrate that is usually used for an information carrier.
Use ordinary paper, cloth, synthetic paper, or films of polyester resin, diacetate resin, triacetate resin, acrylic resin, polycarbonate resin, polyvinyl chloride resin, polyimide resin, cellophane, celluloid, etc. be able to. Furthermore, "base sheet"
Include coated paper or cast coated paper provided with a coating layer in advance, and laminated paper processed by laminating a resin film on the surface of the paper or using a molten resin.

[0004] Further, in the present specification, the term "information carrier" refers to various types of information, such as continuous (for example, continuous paper wound on a roll) or cut sheet (for example, stacked sheets). For example, information that requires confidentiality, confidentiality or concealment, such as personal information and print information, or information that does not necessarily require confidentiality, such as advertisements and advertisements, is handwritten or printed. Means an information medium included in the information medium, for example, in the form of a postcard, an envelope, a business form, a delivery slip, a communication card, a folding card, a superimposed sheet, an information hiding sheet, or the like. . An envelope or the like is not necessarily printed with information, and should be a container of information for containing an information medium. However, in this specification, the envelope is included in the information carrier described above. Further, in this specification, "printing" refers to writing various information, patterns, and the like using any general printing method such as offset printing, gravure printing, or printing using a non-impact printer. Say.

[0005] Among such information carriers, one of the most popular is a so-called confidential postcard. The outline of an information carrier will be described by taking a confidential postcard as an example. Before recording information, the base sheet used for such an information carrier is usually coated with an adhesive called a cold seal adhesive in advance on the surface to be printed of the base sheet and dried. Is formed. Next, information is printed on the coated printing surface by using a printing method such as offset printing, gravure printing, and printing using a non-impact printer. The order of printing and coating may be changed. Further, the printed surface on which the information is printed is overlapped so that the adhesive layer on both surfaces is in contact with the other surface on which the cold seal adhesive is applied and the adhesive layer is formed, and a certain amount or more is applied. Can be bonded by applying pressure. As a result, it is possible to form a laminate in which the secret information is hidden (not visible from the outside), that is, a confidential postcard. This secret information can be read by peeling off the adhered surface again, but the surface once peeled will not adhere unless a certain pressure is applied again, so the secret information is hidden before lamination before peeling. Does not return to the state of the body. As a result, the confidential postcard can maintain confidentiality.

[0006] Such cold seal adhesives are required to have the following basic properties: under normal conditions, no tack is formed on the coated surface on which the adhesive layer is formed; Adhesion and blocking do not occur even when the adhesive layers of the two coated surfaces are overlapped so that both adhesive layers are in contact with each other; by applying a certain pressure or more to the overlap of the adhesive layers Both can be bonded.

[0007] In the present specification, the "normal state" means that no special operation such as pressurizing is applied to the substrate sheet coated with the adhesive. When the coated surfaces applied to the sheets are stacked and left or stored, when the stacked base sheets are pressed strongly by hand, or when the information is printed on those coated surfaces, a low pressure (approximately 7, 7) is applied. 840 N / m ²
Pressure below).

Accordingly, in the present specification, the “cold seal adhesive” is an adhesive which does not cause tack on a coated surface on which an adhesive is applied and an adhesive layer is formed in a normal state. In a normal state, even if the adhesive layers of the two coated surfaces on which the adhesive is applied are overlapped so that the two adhesive layers are in contact with each other, the adhesive does not cause adhesion and blocking. By applying a pressure higher than the pressure at which the two adhesive layers overlap (for example, a pressure exceeding about 7,840 N / m ² and a pressure applied by a currently used mail sealer), An adhesive that can be bonded.

In this specification, these "cold seal adhesives" do not adhere in a normal state,
The property of being able to adhere by applying a certain pressure or more is called "cold seal adhesiveness". Further, in this specification, the force required to release the cold-sealed adhesion is referred to as “cold seal adhesion force”. In this specification, the “adhesive layer” refers to an adhesive layer after a cold seal adhesive is applied and dried. Examples of the cold seal adhesive described above include, for example,
-295335 can be exemplified.

[0010] The cold seal adhesive is required to have additional characteristics in addition to the above basic characteristics depending on the type of the information carrier. Information carrier is a confidential postcard, communication card,
In the case of a form such as a folding card, an overlapping sheet, and an information hiding sheet, the cold seal adhesive includes:
Further, for example, additional properties are required, such as the following: The bond can be released by peeling the bonded base sheets together, usually with the force of a human hand pulling them apart from each other; When the substrate is released, the base sheet is not broken (hereinafter also referred to as “removable”), that is, information on the surface from which the adhesive has been released can be completely read; Do not glue again with enough pressure to apply it manually.

When the information carrier is in the form of an envelope, a business form or the like, the cold seal adhesive is different from the form of a confidential postcard or the like, for example, when the adhesive is released, it can be visually confirmed. (Hereinafter, also referred to as "material destruction") is required.

[0012] Such a cold seal adhesive comprises various components. As one of the components, there is a component (hereinafter, also referred to as “adhesive component”) that imparts adhesiveness to the cold seal adhesive. As an adhesive component, a natural rubber latex or a methyl methacrylate (MMA) -modified natural rubber latex and / or a styrene-modified natural rubber latex obtained by graft polymerization of methyl methacrylate and / or styrene onto natural rubber latex (hereinafter referred to as “conventional modified rubber latex”) Natural rubber latex ") is used.

When natural rubber latex is used as a main component of an adhesive component in a cold seal adhesive, there is an advantage that a cold seal adhesive having excellent cold seal adhesive strength and little tackiness can be obtained. .
However, natural rubber latex has low mechanical stability of an adhesive layer formed, and does not have sufficient adhesion to a base sheet (for example, paper) used for an information carrier and surface strength of a coated surface. There is a problem. Furthermore, if natural rubber latex is used as a main component of an adhesive component in a cold seal adhesive, the natural rubber can be degraded by heat, light, oxygen, ozone, etc. There is also a problem that the force can be deteriorated due to heat and ultraviolet rays during printing or during printing.

In order to solve the problems of the natural rubber latex, the above-mentioned MMA-modified natural rubber latex and / or styrene-modified natural rubber latex are used. It is known that by using these conventional modified natural rubber latexes, mechanical stability can be improved and the surface strength of the coated surface can be enhanced. However, there is no solution to the problem that the cold seal adhesive strength of the cold seal adhesive can be deteriorated by heat, ultraviolet rays, etc. over time or during printing.

Therefore, a cold seal adhesive which can solve the problem of a cold seal adhesive using natural rubber latex and conventional modified natural rubber latex (hereinafter also referred to as “conventional natural rubber latex”) as an adhesive component is At present, it has not been obtained yet. In this specification, the difficulty of deterioration of the cold seal adhesive by heat, the difficulty of deterioration by UV, and the difficulty of deterioration by ozone are referred to as heat resistance, UV resistance, and resistance, respectively. Also called ozone.

[0016]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and the problem is to solve the problem of the conventional cold seal adhesive using the conventional natural rubber-based latex. , Heat, light, oxygen, ozone and the like, the problem of deterioration of the cold seal adhesive force is reduced, preferably substantially eliminated, and further,
Good blocking resistance, cold seal adhesive strength, and printability (related to offset printing, gravure printing, printing with a non-impact printer, etc.)
An object of the present invention is to provide a cold seal adhesive having high overall performance, which can easily adjust these properties appropriately. Further, it is an object of the present invention to provide an adhesive site where such a cold seal adhesive is applied to form an adhesive layer. In particular, it is to provide an information carrier having such an attachment site.

[0017]

Means for Solving the Problems The present inventors have conducted various studies on the resin used as an adhesive component of the cold seal adhesive, and as a result, as described in detail below, have been proposed in place of the conventional natural rubber latex. In addition, by using a specific modified natural rubber latex, it is possible to obtain a good cold seal adhesive such as cold seal adhesive strength and blocking resistance while at least alleviating the problems caused by using the conventional natural rubber latex. This has led to the completion of the present invention.

According to one aspect of the present invention, there is provided a novel cold seal adhesive, which comprises modifying a modified natural rubber latex obtained by graft polymerization of an acrylate compound onto a natural rubber latex, to obtain a complete adhesive. A cold seal adhesive comprising from 20 to 70% by weight of the composition. Further, according to another aspect of the present invention, there is provided an adhesive portion on which the cold seal adhesive according to the present invention is applied to form an adhesive layer. In accordance with another aspect of the present invention, there is provided a confidential postcard having the above-mentioned bonding site.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The cold seal adhesive of the present invention is water-based, and has a modified natural rubber latex (hereinafter referred to as "resin (A)") obtained by graft-polymerizing an acrylate compound onto a natural rubber latex as an adhesive component. : Acrylic acid ester-modified natural rubber latex), and the resin (A) accounts for 20 to 70% by weight of the total composition of the adhesive.

In the present specification, the term "water-based" as used as the cold seal adhesive refers to an acryl-modified natural rubber latex contained in the cold seal adhesive, and other resins and fine particle fillers described below which can be contained in the cold seal adhesive. And additives and the like are present in an aqueous medium, and include a state in which these resins and the like are dissolved and / or dispersed in the aqueous medium. In addition, throughout this specification, parts by weight and% by weight are based on a part excluding an aqueous medium unless otherwise specified. Therefore, in the cold seal adhesive of the present invention, the resin (A) accounts for 20 to 70% by weight based on the total weight of the adhesive, excluding the aqueous medium (100% by weight). And an adhesive having a fluid form (for example, an emulsion form, a latex form) including a state in which a resin or the like is dissolved and / or dispersed in an aqueous medium.

As used herein, the term "aqueous medium" refers to general water such as distilled water and ion-exchanged water.
It may contain a water-soluble or water-dispersible organic solvent, a monomer, an oligomer, etc., as long as it does not adversely affect the properties of the cold seal adhesive of the present invention, and is usually used in the production of the resin (A). May be included.

In the present invention, the resin (A): acrylate modified natural rubber latex is an acrylate modified natural rubber latex obtained by graft polymerization of an acrylate compound onto a natural rubber latex. Here, the acrylate compound is an ester compound obtained from acrylic acid and a compound having a hydroxyl group, and is particularly limited as long as the cold seal adhesive intended for the present invention can be obtained. is not.

Examples of the acrylate compound include, for example, the following compounds: methyl acrylate,
Ethyl acrylate, propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, isononyl acrylate, dodecyl acrylate, tridecyl acrylate, octadecyl acrylate, etc. Alkyl acrylates having an alkyl group which may contain a branch of: cycloalkyl acrylates having a cycloalkyl group which may contain a substituent such as cyclohexyl acrylate; hydroxyethyl acrylate and hydroxypropyl acrylate Alkyl acrylates having a hydroxyl group-containing alkyl group such as glycidyl acrylate; Acrylic acid alkyl esters having an alkyl group containing shea group.

The acrylate compound is preferably at least one selected from alkyl acrylates having an alkyl group which may contain a branch. Further, in order to obtain sufficient polymerization stability in the graft polymerization reaction. The alkyl group, which may contain a branched alkyl acrylate, has 1 to 1 carbon atoms.
It is preferably 10. Further, at least one selected from butyl acrylate, ethyl acrylate, and 2-ethylhexyl acrylate is particularly preferable as the acrylate compound. The above-mentioned acrylic ester compounds can be used alone or in combination as appropriate according to the properties of the intended cold seal adhesive.

The acrylate compound includes acrylamides such as acrylamide and methylolamide acrylate, and the amides can be used alone or in combination.

The acrylate compound is graft-polymerized to the natural rubber latex to give the resin (A). In this case, 0.1 to 20 parts by weight of the acrylate compound per 100 parts by weight of the natural rubber latex Is preferably graft-polymerized to natural rubber latex, more preferably 0.5 to 10 parts by weight of an acrylate compound is graft-polymerized, and 1 to 5 parts by weight of an acrylate compound is graft-polymerized. Is particularly preferred.

It is preferable that the natural rubber latex is further polymerized with another polymerizable monomer in addition to the above-mentioned acrylate compound. Here, the "other polymerizable monomer" is a compound that can be graft-polymerized to the natural rubber latex described above, and generally refers to a compound containing a functional group having an ethylenic double bond, For example, alkyl methacrylates such as methyl methacrylate, styrene, and acrylonitrile can be exemplified, and alkyl methacrylates are preferable.

The above-mentioned other polymerizable monomers can be used alone or in combination as appropriate according to the intended properties of the cold seal adhesive. Natural rubber latex, in addition to the acrylate compound described above, further,
When polymerizing another polymerizable monomer, 1 to 50 parts by weight of the total of the acrylate compound and the other polymerizable monomer is 100 parts by weight of the natural rubber latex. The graft polymerization is preferably performed, and more preferably 3 to 30 parts by weight is graft-polymerized. It is preferable that the acrylic acid ester compound and the other polymerizable monomer are simultaneously graft-polymerized to the natural rubber latex, but one of them may be polymerized first depending on the purpose.

The above-mentioned resin (A): "natural rubber latex" used in the production of acrylic acid ester-modified natural rubber latex refers to an emulsion of naturally occurring rubber, and is usually called "natural rubber latex". It is not particularly limited as long as it can be used as an adhesive, as long as the intended cold seal adhesive of the present invention can be obtained. Further, as long as the cold seal adhesive targeted by the present invention can be obtained, modified natural rubber latex and / or styrene-modified natural rubber latex which have been conventionally used in cold seal adhesives can be used. Rubber latex is also included in the “natural rubber latex” used in the production of the resin (A). Natural rubber latex can be used alone or in combination.

In the present invention, the resin (A) can be prepared by appropriately selecting the composition and amount of an acrylate compound which polymerizes into a natural rubber latex and other polymerizable monomers used as required. : The properties of acrylic ester-modified natural rubber latex can be adjusted. Therefore, the heat resistance, UV resistance, ozone resistance,
Mechanical stability, cold seal adhesiveness, etc. can be easily adjusted.

Resin (A): The acrylate-modified natural rubber latex is prepared by using the above-mentioned acrylate ester by appropriately using a catalyst or the like, using a conventional method usually used as a method for producing a modified natural rubber latex. Compound,
Further, it can be obtained by graft-polymerizing another polymerizable monomer used as necessary to the natural rubber latex. Reaction time of polymerization reaction, reaction temperature, type and concentration of acrylic acid ester compound, and other polymerizable monomers used as required, stirring speed, type and concentration of catalyst, type and concentration of emulsifier, etc. The reaction conditions can be appropriately selected according to the characteristics of the target resin (A) and the like.

The term "catalyst" as used herein means a compound capable of causing a graft polymerization reaction of an acrylate compound by adding a small amount. For example, ammonium persulfate, sodium persulfate, potassium persulfate, t-butyl hydroperoxide, t-butyl peroxybenzoate, 2,2-azobisisobutyronitrile (AIB
N), 2,2-azobis (2-amidinopropane) dihydrochloride, 2,2-azobis (2,4-dimethylvaleronitrile), and the like.
-Butyl hydroperoxide and t-butyl peroxybenzoate are preferred. In order to carry out the polymerization reaction at a low temperature, it is preferable to combine the polymerization reaction catalyst with a reducing agent such as tetraethylenepentamine.

In the present invention, with respect to the resin (A): acrylate modified natural rubber latex as described above, the swelling ratio of the film formed from the resin (A) is 2
It is preferably 0 times or less. Here, the method for forming the film is not particularly limited as long as it is a method used for forming a conventional natural rubber-based latex film, and any method may be used. it can. As a method of forming such a film, for example, 50 ° C.
Then, a method of heating and drying for 24 hours to obtain a film having a film thickness of about 2 mm can be exemplified.

Further, in the present specification, “swelling ratio of film”
As described in detail in Examples described later, a film before dipping in toluene (2.5 cm × 2.5 cm × 2
mm) as a reference (1) and refers to the magnification of the weight of the film after immersion in toluene (20 ° C., 24 hours).
The swelling ratio of the resin (A) is preferably 20 times or less, more preferably 15 times or less, and particularly preferably 10 times or less. The swelling ratio of the resin (A) is usually 5 to 15.

The cold seal adhesive of the present invention comprises the resin (A): acrylic acid ester-modified natural rubber latex in an amount of 20 to 70% by weight in the total composition of the adhesive, but contains 30 to 60% by weight. Preferably. Here, “wt%” is based on a portion not containing an aqueous medium, as described above. Needless to say, the acrylic acid ester-modified natural rubber latex can be used alone or in combination as the resin (A).

The cold seal adhesive of the present invention may further comprise resin (B): a polyolefin resin. Here, “resin (B): polyolefin resin”
Is a compound that is blended with the cold seal adhesive of the present invention for the purpose of imparting abrasion resistance, blocking resistance, and removability, and may be a commonly used polyolefin-based resin and may be water-based. There is no particular limitation as long as it does not adversely affect the cold seal adhesive of the present invention. The “resin (B)” to be aqueous refers to a polyolefin-based resin that can be present in an aqueous medium, and is a resin (B) dissolved in an aqueous medium and / or dispersed (for example, emulsion) Resin (B).

As such resin (B), for example, polyethylene, polypropylene, and halogenated polyolefin such as chlorinated polyethylene and chlorinated polypropylene are modified (for example, carboxyl group, sulfonate group, phosphate group, Resin modified by a hydrophilic group such as a hydroxyl group or an amino group), a resin which can be present in an aqueous medium by using an emulsifier or a water-soluble polymer, and a resin which can be present in an aqueous medium. The above-mentioned resin dispersed in the above can be exemplified. Resin (B)
In particular, an aqueous dispersion of polyethylene is preferable. Such a resin (B) can be produced by a known method, but a commercially available resin can be used, and for example, Chemipearl W308 (trade name) manufactured by Mitsui Chemicals, Inc. can be exemplified.

Resin (B): The softening point of the polyolefin resin is preferably 40 ° C. or higher, more preferably 70 ° C. or higher, and particularly preferably 100 ° C. or higher. Here, "resin (B)
"Softening point" means a softening point measured using a ring and ball method softening point test shown in JIS K2207.

Further, the average particle size of the resin (B): polyolefin resin is preferably 0.1 to 20 μm, and 0.5 to 20 μm.
It is particularly preferred that the thickness be 15 μm. Here, the “average particle size of the resin (B)” refers to a particle size measured by a Coulter counter method. Polyolefin-based resins can be used alone or in combination as the resin (B). When the cold seal adhesive of the present invention comprises the resin (B), the total amount of the adhesive is 100% by weight.
The resin (B) preferably contains 0 to 30% by weight, and particularly preferably 3 to 25% by weight.

The cold seal adhesive of the present invention is a resin other than the resin (C): the resins (A) and (B), and has a Tg of-
It may further comprise at least one selected from resins having a temperature of 30 ° C. or higher. In the present invention, "resin (C): a resin other than resins (A) and (B), wherein Tg is-
At least one selected from resins having a temperature of 30 ° C. or higher ”
Is a compound that is added to the cold seal adhesive of the present invention for the purpose of imparting blocking resistance, adhesion to a base sheet, and abrasion resistance, and is other than resins (A) and (B). The resin may have a Tg of −30 ° C. or higher and be at least one kind of resin generally used for a cold seal adhesive. The resin (C) is not particularly limited as long as it can be water-based and does not adversely affect the cold seal adhesive of the present invention. still,
The term “aqueous resin (C)” refers to a resin (C) present in an aqueous medium, which is dissolved in an aqueous medium and / or dispersed in an aqueous medium (for example, Emulsion type or latex type).

Examples of such a resin (C) include vinyl resins, synthetic rubber resins, and water-soluble polymers. Here, the “vinyl resin” is a polymer produced by addition polymerization of a vinyl compound, and includes, for example, vinyl acetate, styrene, ethylene, (meth) acrylic acid, (meth) acrylates, acrylonitrile, And polymers obtained by addition polymerization of acrylamide alone or in combination.

Examples of the "synthetic rubber-based resin" include styrene-butadiene copolymer (SBR), acrylonitrile-butadiene copolymer (NBR), and copolymers of acrylates and butadiene (MBR). it can. As "water-soluble polymer", for example, starch,
Casein, cellulose, polyvinyl alcohol, and modified products thereof (for example, cationic modified products, acid-modified products,
And silane-modified products).

Such a resin (C) can be produced by a known method, but a commercially available resin can be used. For example, as a synthetic rubber resin, Nipol manufactured by Zeon Corporation can be used.
LX416 (trade name) and Nipol SX1706 (trade name) manufactured by Zeon Corporation as vinyl resin can be exemplified.

The Tg of the resin (C) is -30 ° C. or higher, and particularly preferably -20 ° C. or higher. Here, the resin (C)
The Tg in the above refers to a temperature described below measured using a differential scanning calorimeter (DSC). A DSC curve is obtained by measuring the heat capacity of the resin (C) using DSC. The DSC curve drawn at the point where the slope of the DSC curve of the step change portion based on the glass transition becomes the maximum, and the straight line obtained by extending the low temperature side baseline of the step change portion based on the glass transition to the high temperature side of the DSC curve. The temperature at the intersection with the tangent to the curve is defined as Tg of the resin (C).

The resin (C) is preferably in the form of an emulsion, but may be dissolved in an aqueous medium. Resins other than the resins (A) and (B) and having a Tg of −30 ° C. or higher can be used alone or in combination as the resin (C). When the cold seal adhesive of the present invention comprises the resin (C), the cold seal adhesive preferably contains the resin (C) in an amount of 0 to 80% by weight based on 100% by weight of the entire adhesive,
It is particularly preferable that the resin (C) is contained in an amount of 1 to 60% by weight.

The cold seal adhesive of the present invention may further comprise a fine particle filler. Here, "fine particle filler" refers to a fine particle filler usually used in cold seal adhesives, for example, silica gel, hollow silica, mica, calcium carbonate, kaolin, talc, diatomaceous earth, urea-based resin, styrene beads , Clay, cereal starch, modified starch and the like. Further, the fine particle filler is usually a particle, and its size is not particularly limited as long as the intended performance of the present invention is exhibited. These particulate fillers alone or in combination,
It can be appropriately selected and used according to the required characteristics. By using a fine particle filler, it is possible to easily and suitably adjust properties such as cold seal adhesive strength, blocking resistance, printability, abrasion resistance, and adhesion to a base sheet required as a cold seal adhesive. Can be.

In the present invention, various additives can be added to the cold seal adhesive. Here, the “additive” refers to an additive usually used as necessary in a cold seal adhesive, for example, a lubricant, a printability improver, an antioxidant, an ultraviolet absorber, a radical scavenger, a conductive agent, a fluorescent agent. Examples include paints, coloring dyes, stabilizers, defoamers, fungicides, bacteriostats, thickeners, humectants, and the like.

Further, in the present invention, a tackifier such as rosin can be added in order to improve the cold seal adhesive strength of the cold seal adhesive.
These additives can be used singly or in combination, and can be appropriately selected and used according to the required properties. By using these additives, a cold seal excellent in printability, stability, and antifungal properties can be obtained. An adhesive can be provided.

The cold seal adhesive of the present invention is suitable as an adhesive for bonding a base sheet by applying pressure. The present invention further provides an adhesion site in which the above cold seal adhesive is applied to a base sheet and dried to form an adhesive layer. In the present specification, "adhesion site"
The term refers to a portion where a cold seal adhesive is applied and dried to form an adhesive layer, but is not yet bonded by applying pressure.

In one embodiment of the present invention, a cold seal adhesive is applied to the surface of the base sheet to be printed and dried to form an adhesive layer, and the information is printed on the surface to be printed. Then, a part of the printed surface and the other part are folded so as to be in contact with each other, and the folded adhesive layers are overlapped so as to be in contact with each other, thereby providing an adhesive portion for crimping the two together.

In another embodiment of the present invention, a cold seal adhesive is applied to the surface of the substrate sheet to be printed and dried to form an adhesive layer, and the information is printed on the surface to be printed. Then, the printed surface is coated with a cold seal adhesive and dried so that the other surface on which the adhesive layer is formed and the adhesive layer on both surfaces are in contact with each other. Provides an adhesive site for crimping.

Here, the “base sheet” is as described above. Further, "the other surface on which the cold seal adhesive is applied and dried to form an adhesive layer" means that the cold seal adhesive of the present invention is applied and dried to form an adhesive layer. Any other surface (usually, the surface of the base sheet), for example, such a surface may be printed before coating, or an adhesive formed by coating. May be printed on top of the layer. Specifically, it refers to a surface that has been subjected to coating → printing, printing → coating, or only coating.

In the present specification, the term “coating” refers to a method of applying a cold seal adhesive, as long as it is a coating method conventionally used in the art. For example, a roll coater, a bar coater, a blade coater, an air knife coater, a rod blade coater, a gravure roll coater and the like can be exemplified. Further, "coating" includes methods used to apply cold seal adhesives, for example,
Coating and spraying can also be used.

The term "drying" refers to a method for drying the cold seal adhesive, which can be used without any particular limitation as long as it is a drying method conventionally used, for example, natural drying, hot air Drying, high-frequency drying and the like can be exemplified.

Further, the term "pressure bonding" means that the two surfaces on which an adhesive is applied and dried to form an adhesive layer are brought into contact with each other in a manner similar to the processing conventionally used for cold sealing. And applying pressure and, if necessary, heat as necessary to bond the two surfaces together. Therefore, "crimping"
It also means that pressure is applied to the bonding portion of the base sheet to bond it integrally.

Further, the present invention provides the above-mentioned bonding site bonded by applying pressure. Therefore, the above-mentioned bonded portion bonded is also included in the present invention. The cold seal adhesive of the present invention can be used by using the same method as a conventionally used cold seal adhesive, and by using such a method, an adhesive portion can be provided on the base sheet. Therefore, the present invention is intended to provide 20 to 70% by weight of the entire adhesive.
Resin (A): Since a cold seal adhesive containing an acrylate-modified natural rubber latex is used, problems caused by using a conventional cold seal adhesive containing a natural rubber-based resin as an adhesive component are alleviated, which is preferable. Provides an adhesion site which is substantially removed and further exhibits excellent performance in adhesion and blocking resistance.

Further, an information carrier having such an adhesion site is provided. Such information carriers are particularly preferably in the form of confidential postcards, envelopes, and business forms. However, here, the base sheet used for the information carrier, the conditions for applying the cold seal adhesive, the thickness of the adhesive layer provided on the base sheet, and the crimping conditions for the information carrier are as follows:
It is appropriately selected according to the intended information carrier (including any one that requires the releasable or material-destructive properties of the cold seal adhesive).

As described above, the cold seal adhesive of the present invention has at least one selected from heat resistance, UV resistance and ozone resistance, and further has blocking resistance and cold seal adhesive strength. And an adhesive layer having good printability (related to offset printing, gravure printing, printing with a non-impact printer, etc.) can be formed. This is considered for the following reason.

It is known that natural rubber latex is a linear polymer, and that the molecular structure has an ethylenic double bond. The fact that the polymer chain of the natural rubber latex is linear and has an ethylenic double bond is considered to be one of the causes of the low chemical stability of the natural rubber latex.

When an acrylate compound is graft-polymerized to a natural rubber latex, the acrylate compound undergoes addition polymerization to an ethylenic double bond present in a chain of the natural rubber. Is believed to provide a cross-linked structure between the chains. Therefore, it is considered that the number of ethylenic double bonds in the natural rubber decreases and the generation of a crosslinked structure between the chains of the natural rubber makes the molecular chains more difficult to move. As a result, in the resin (A): acrylic acid ester-modified natural rubber latex, an ethylenic double bond that causes deterioration of the natural rubber latex due to heat, UV, ozone, or the like is converted into a single bond. It is considered that the polymer is more stabilized and that the natural rubber chain is more stabilized physically by providing a crosslinked structure.

On the other hand, when a conventionally used monomer such as methyl methacrylate and styrene is graft-polymerized to a natural rubber latex, the polymer chain of the natural rubber is changed into a polymer chain of the natural rubber like the above-mentioned acrylate compound. Methyl methacrylate, styrene, and the like may be addition-polymerized to the existing double bond, but it is thought that there are more cases where methyl methacrylate, styrene, and the like are addition-polymerized with each other. That is, in the conventional modified natural rubber latex, it is considered that polymethyl methacrylate and polystyrene are formed in the natural rubber independently of the natural rubber, for example, like a sea-island. Therefore, the mechanical stability of the conventional modified natural rubber latex was improved by graft polymerization of methyl methacrylate and styrene, etc., onto natural rubber latex because of the physical stability of polymethyl methacrylate and polystyrene itself. It is considered that this is because the rubber latex was stabilized, and the chemical stability of the natural rubber latex itself was not necessarily improved.

As described above, the fact that the chemical structure of the resin (A) is different from the chemical structures of the natural rubber latex and the conventional modified rubber latex can be understood by examining the respective swelling ratios. The swelling ratio is considered to correspond to the crosslink density of each polymer chain. It is considered that the smaller the value is, the more the polymer chains are crosslinked and the more difficult it is to move. According to the study of the present inventors, the swelling ratio of the natural rubber latex and the conventional modified natural rubber latex are usually about 40 times, while the swelling ratio of the resin (A) is smaller than 40 times. . Therefore, while the difficulty of movement of the polymer chains of natural rubber latex and conventional modified natural rubber latex is comparable,
It is considered that the polymer chains of the resin (A) are harder to move than those. The difficulty in the movement of the polymer chain of the resin (A) is attributed to the fact that the acrylate compound is addition-polymerized to the ethylenic double bond present in the natural rubber chain, and the acrylate compound is converted to the natural rubber chain. It is considered that this is expressed by providing a crosslinked structure between the two.

Since the swelling ratio of the conventional modified natural rubber latex is substantially the same as the swelling ratio of the natural rubber latex itself as described above, even if methyl methacrylate and styrene are graft-polymerized to the natural rubber latex, It hardly changes the difficulty of movement of the chain itself, and it is considered that no significant change has occurred in the molecular structure itself of the polymer of natural rubber. As a result, it is considered that methyl methacrylate and styrene are substantially polymerized with each other.

Accordingly, in the cold seal adhesive of the present invention, the chemical structure of the polymer chain of the natural rubber latex is converted, and essentially the natural rubber itself can be chemically and physically stabilized. Therefore, it is considered that at least one selected from heat resistance, UV resistance, and ozone resistance of the resulting adhesive layer is improved.

Although the cold seal adhesive of the present invention is considered to have excellent properties for the reasons described above, the cold seal adhesive of the present invention is not limited by these reasons. .

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EXAMPLES Hereinafter, the present invention will be described specifically and in detail with reference to working examples and comparative examples. However, these examples are only one aspect of the present invention, and the present invention is not limited to these examples. Absent. In the description of the examples, unless otherwise specified, the portion not containing the aqueous medium is based on parts by weight and% by weight.

Example 1 Production of Cold Seal Adhesive A three-necked flask equipped with a stirrer, thermometer and reflux condenser was placed
100 parts by weight of natural rubber latex, 20 parts by weight of distilled water, and 0.2 parts by weight of t-butyl hydroperoxide as a catalyst were added and stirred to obtain a mixture. On the other hand, 5 parts by weight of butyl acrylate, 5 parts by weight of methyl methacrylate, and 0.4 parts by weight of sodium polyoxyethylene alkylphenyl sulfate as an emulsifier were added to 5 parts by weight of distilled water and stirred to obtain an emulsion. This emulsion was added to the above mixture, the temperature was raised to 40 ° C., and then 0.4 parts by weight of tetraethylpentamine as a reducing agent was added to the mixture over 30 minutes, whereby the acrylic ester-modified natural product of Example 1 was added. A rubber latex was obtained.

The acrylic acid ester-modified natural rubber latex of Example 1 was dried by heating at 50 ° C. for 24 hours.
A film having a thickness of about 2 mm was obtained. The size of this film is 2.
The size was 5 cm × 2.5 cm × 2 mm, and the weight was weighed. 20
After immersion in toluene at 24 ° C. for 24 hours, the weight was weighed. The swelling ratio is obtained by (weight after immersion in toluene) / (weight before immersion in toluene), and the swelling ratio of the film formed from the acrylate-modified natural rubber latex of Example 1 is
It was 7 times.

To 100 parts by weight of the acrylate-modified natural rubber latex of Example 1 are added 100 parts by weight of a particulate filler (comprising amorphous silica, starch and calcium carbonate) and 15 parts by weight of auxiliaries. Thus, a cold seal adhesive of Example 1 was obtained. Thus, the cold seal adhesive of Example 1 comprises 46.5% by weight of the acrylate modified rubber latex of Example 1.

Evaluation of Cold Seal Adhesive Preparation of Coated Sheet 130 g / m ² of high quality paper was used as a base sheet, and the coated amount after drying on one side of this high quality paper was 10 g / m ² . The cold seal adhesive of Example 1 was applied and dried to obtain a coated sheet having an adhesive layer formed thereon (hereinafter also referred to as “coated sheet of Example 1”).

Evaluation of Cold Seal Adhesion The cold seal adhesion was evaluated by measuring the adhesive force (cold seal adhesive force) when the coated sheet of Example 1 was pressure-bonded and peeled off. The coated sheet of Example 1 was folded in two so that the adhesive layers were overlapped, and pressure-bonded using a mail sealer for pressure bonding while changing the gap between the rollers in various ways. 3
After standing for 0 minutes, a T-type peeling test was performed using a tensile tester at a pulling speed of 300 mm / min, and the force required for peeling (cold seal adhesive force) was measured. Example 1 The cold seal adhesive strength of the cold seal adhesive is shown in Table 1.

Evaluation of Heat Resistance The coated sheet of Example 1 was placed in an oven at 105 ° C. for 30 minutes.
The heat treatment was performed by holding for a minute. Then 2
The coated sheet cured for 4 hours was folded in two so that the adhesive layers were overlapped, and pressed using a mail sealer with a gap of 220 μm between rollers. After leaving the coated sheet pressed for 30 minutes, a T-peel test was performed using a tensile tester at a tensile speed of 300 mm / min, and the force required for peeling was measured. Cold coated adhesive strength of coated sheet without heat treatment is 10
The holding ratio of the cold seal adhesive strength of the coated sheet after the heat treatment at 0% was determined. The results are shown in Table 1.

Evaluation of UV Resistance 15 W of U was applied to the adhesive-coated surface of the coated sheet of Example 1.
By irradiating UV for 2 hours using a V lamp,
UV irradiation treatment was performed. Thereafter, the coated sheet cured for 24 hours was folded in two so that the adhesive layers were overlapped with each other, and pressed using a mail sealer with a gap of 220 μm between rollers. After leaving the press-coated coated sheet for 30 minutes, using a tensile tester, 300 mm /
A T-peel test was performed at a tensile speed of 1 minute, and the force required for peeling was measured. Assuming that the cold seal adhesive force of the coated sheet not subjected to the UV irradiation treatment was 100%, the retention rate of the cold seal adhesive force of the coated sheet after the heat treatment was determined. The results are shown in Table 1.

Example 2 Example 1 was repeated except that 5 parts by weight of butyl acrylate and 5 parts by weight of methyl methacrylate were replaced by 1 part by weight of butyl acrylate and 4 parts by weight of methyl methacrylate. The cold seal adhesive of Example 2 was obtained by using the same method as described in (1).
Using the same method as described in Example 1, Example 2
Of cold seal adhesives were evaluated. The results are shown in Table 1.

Example 3 Example 1 was repeated except that 1 part by weight of ethyl acrylate and 4 parts by weight of methyl methacrylate were used in place of 5 parts by weight of butyl acrylate and 5 parts by weight of methyl methacrylate. The cold seal adhesive of Example 3 was obtained by using the same method as described in (1).
Using the same method as described in Example 1, Example 3
Of cold seal adhesives were evaluated. The results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated, except that 5 parts by weight of butyl acrylate and 5 parts by weight of methyl methacrylate were replaced by 25 parts by weight of methyl methacrylate. Using the method, a cold seal adhesive of Comparative Example 1 was obtained. Using the same method as that described in Example 1, the cold seal adhesive of Comparative Example 1 was evaluated. The results are shown in Table 1.

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[Table 1] a) BA is butyl acrylate, EA is ethyl acrylate, MMA is methyl methacrylate, and the unit is:
Parts by weight used per 100 parts by weight of natural rubber latex. b) Swelling ratio = weight after immersion in toluene / weight before immersion in toluene. c) the gap between the rollers is 280, 260, 240
, And 220 μm, respectively. The unit is gf / 25 mm. d) Retention rate of cold seal adhesive strength (gap between rollers is 220 μm) after heat treatment. e) Retention rate of cold seal adhesive strength (gap between rollers is 220 μm) after UV irradiation.

As to the cold seal adhesive strength, from the values measured by changing the gap between the rollers, both of the cold seal adhesives of the examples and the comparative examples were values having no practical problems. Regarding the heat resistance and the UV resistance, it is understood that the retention of the cold seal adhesive force of the cold seal adhesive of the example is greatly improved as compared with the cold seal adhesive of the comparative example.

[0079]

The cold seal adhesive of the present invention comprises an acrylic ester modified natural rubber latex,
Compared to the case using conventional cold seal adhesive,
At least one selected from heat resistance, UV resistance, and ozone resistance is improved, and further, blocking resistance, cold seal adhesive strength, and printability (offset printing,
Gravure printing, printing with a non-impact printer, etc.), and these properties can be easily adjusted as appropriate. Thus, an adhesive layer having high overall performance is formed. Furthermore, an adhesive site provided with such a layer of adhesive is provided, and in particular, an information carrier having such an adhesive site is provided.

Claims (10)

[Claims] 1. A cold seal adhesive comprising 20 to 70% by weight of a modified natural rubber latex obtained by graft polymerization of an acrylate compound onto a natural rubber latex. 2. The cold seal adhesive according to claim 1, wherein the modified natural rubber latex is obtained by graft polymerization of 0.1 to 20 parts by weight of an acrylate compound per 100 parts by weight of the natural rubber latex. 3. The cold seal adhesive according to claim 1, wherein the acrylate compound is at least one selected from alkyl acrylates having an alkyl group having 1 to 10 carbon atoms. 4. The cold seal adhesive according to claim 1, wherein the acrylate compound is at least one selected from butyl acrylate, ethyl acrylate, and 2-ethylhexyl acrylate. 5. The modified natural rubber latex according to claim 1, wherein a swelling ratio of a film formed therefrom is 20 times or less.
The cold seal adhesive according to any one of the above. 6. The cold seal adhesive according to claim 1, further comprising a polyolefin resin. 7. An adhesive portion formed by applying the cold seal adhesive according to any one of claims 1 to 6 to form an adhesive layer. 8. A cold seal adhesive is applied to the surface of the base sheet to be printed and dried to form an adhesive layer, and information is printed on the surface to be printed. 8. The bonding part according to claim 7, wherein the part is folded so that the other part is in contact with each other, and the folded two adhesive layers are overlapped so as to be in contact with each other, and the two parts are crimped together. 9. A cold seal adhesive is applied to the surface of the base sheet to be printed and dried to form an adhesive layer. After printing information on the surface to be printed, the printed surface is removed. Claims: A cold seal adhesive is coated and dried, and the other surface on which the adhesive layer is formed is overlapped with the adhesive layer on both surfaces so as to be in contact with each other, and the two are integrally pressed. 8. The adhesion site according to 7. 10. A confidential postcard having the adhesion site according to claim 8 or 9.