JP3495981B2 - Cold seal adhesive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is
An adhesive that does not cause 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 surface is laminated so that the adhesive layers of both are in contact with each other, it is an adhesive that does not cause adhesion and blocking, but by applying a certain pressure or more to both of the laminated surfaces, It relates to a cold seal adhesive capable of adhering surfaces.

Further, it relates to an adhesive site coated with such a cold seal adhesive to form a layer of adhesive.
In particular, regarding an information carrier having such an adhesive portion, various information, for example, information that requires confidentiality, concealment or concealment, or necessarily confidentiality is required on a continuous or single-piece base sheet. The present invention relates to an information carrier in the form of a postcard, an envelope, a business form, a delivery slip, a communication card, a folding card, a stacking sheet, an information concealing sheet, etc.

[0003]

2. Description of the Related Art In recent years, various information, for example, information requiring confidentiality, concealment or concealment of personal information, etc., on a continuous or single-cut base sheet, or advertisements, advertisements, etc. Information that does not require confidentiality is printed,
Information carriers in the form of postcards, envelopes, delivery slips, communication cards, folding cards, overlay sheets, information concealment sheets, etc. are becoming popular. In the present specification, the “base sheet” refers to a sheet-shaped base material that is usually used for information carriers, and as the base sheet, for example,
Ordinary paper, cloth, synthetic paper, or polyester resin, diacetate resin, triacetate resin, acrylic resin, polycarbonate resin, polyvinyl chloride resin, polyimide resin, cellophane, celluloid film, etc. be able to. Furthermore, "base sheet"
Includes coated paper or cast coated paper on which a coat layer is provided in advance, laminated paper processed by laminating a resin film on the surface of the paper, or processed with a molten resin.

Further, in the present specification, the "information carrier" means various information on a continuous (for example, continuous paper wound on a roll) or single-cut (for example, stacked sheets) substrate sheet. 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 a medium of information contained in, for example, a medium such as a postcard, an envelope, a business form, a delivery slip, a communication card, a folding card, a stacking sheet, and an information hiding sheet. . It should be noted that an envelope or the like is not necessarily printed with information, and should be called an information container for containing an information medium, but in the present specification, it is included in the above information carrier. Further, in this specification, “printing” means to write various information and patterns, for example, using any general printing method such as offset printing, gravure printing, or printing using a non-impact printer. Say.

Among such information carriers, one of the most popular is the so-called confidential postcard. An information carrier will be outlined using a confidential postcard as an example. The base sheet used for such an information carrier is usually coated with an adhesive called a cold seal adhesive on the surface of the base sheet to be printed and dried before the information is recorded. Layers are formed. Next, information is printed on the coated printing surface by using a printing method such as offset printing, gravure printing, or printing using a non-impact printer. The order of printing and coating may be mixed. Further, the printed surface on which the information is printed is overlaid so that the adhesive layer on both surfaces is in contact with the other surface on which the adhesive layer is formed by applying the cold seal adhesive, and the thickness is kept above a certain level. It can be bonded by applying pressure. As a result, it is possible to form a laminate in which the confidential 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 peeled surface does not adhere unless pressure is applied again more than a certain level, so the secret information is hidden before lamination. Does not return to physical condition. As a result, the confidential postcard can be kept confidential.

Such cold seal adhesives are required to have the following basic properties: Under normal conditions, the coated surface on which the adhesive layer is formed does not tack; under normal conditions Adhesion and blocking do not occur even if the adhesive layers on the two coated surfaces are laminated so that the adhesive layers contact each other; by applying a certain pressure or more to the overlapping of the adhesive layers. Both can be bonded.

In the present specification, the "normal state" means that no special operation such as pressurization is applied to a base sheet coated with an adhesive, for example, a cold seal adhesive is used as a base. When the coated surfaces coated on the sheets are stacked and left or stored, when the stacked base sheets are strongly pressed by hand, or when the information is printed on the coated surfaces, a low pressure (about 7, 840 N / m ²
When the following pressure) is applied, etc.

Therefore, in the present specification, the "cold seal adhesive" is an adhesive which, in a normal state, does not cause tack on the coated surface on which the adhesive is applied to form the adhesive layer, In a normal state, it is an adhesive that does not cause adhesion and blocking even when two adhesive layers coated with an adhesive are stacked so that the two adhesive layers are in contact with each other. By applying a pressure equal to or 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 the mail sealer currently used), both of them are applied. An adhesive that can be bonded.

[0009] In the present specification, these "cold seal adhesives" do not adhere under normal conditions,
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 the present specification, the “adhesive layer” refers to the adhesive layer after the cold seal adhesive is applied and dried. As the cold seal adhesive as described above, for example, Japanese Patent Laid-Open No.
The cold seal adhesive disclosed in JP-A-295335 can be exemplified.

The cold seal adhesive is required to have additional characteristics in addition to the above basic characteristics depending on the type of information carrier. Information carriers are confidential postcards, communication cards,
When it is in the form of a folding card, a stacking sheet, an information concealing sheet, etc., the cold seal adhesive contains
In addition, for example, the following additional properties are required: The adhesion can be released by peeling the base sheets at the adhesion points with a force that is usually pulled by a person so that they are separated from each other; When releasing, the base sheet is not destroyed (hereinafter also referred to as "removable"), that is, the information of the surface where the adhesion is released can be completely read; Do not re-glue under the pressure that a person can apply by hand.

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 case of the confidential postcard or the like in that it can be visually confirmed when releasing the adhesion. It is required that the base sheet (1) be destroyed (hereinafter also referred to as "material destruction").

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. Methyl methacrylate (MMA) -modified natural rubber latex and / or styrene-modified natural rubber latex (hereinafter referred to as "conventional modified"), which is mainly obtained by graft-polymerizing natural rubber latex or methyl methacrylate and / or styrene onto the natural rubber latex as an adhesive component. (Also referred to as "natural rubber latex") is used.

The natural rubber latex has the advantage that when it is used as a main component of an adhesive component in a cold seal adhesive, a cold seal adhesive having excellent cold seal adhesive strength and less tack can be obtained. .
However, the natural rubber latex has low mechanical stability of the formed adhesive layer, and does not have sufficient adhesion to a base sheet (for example, paper) used for an information carrier and sufficient surface strength of a coated surface. There is a problem. In addition, when natural rubber latex is used as a main component of an adhesive component in a cold seal adhesive, natural rubber can be deteriorated by heat, light, oxygen, ozone, etc. There is also a problem that the force may deteriorate due to heat with time or printing and ultraviolet rays.

Therefore, in order to solve the problems of natural rubber latex, the above-mentioned MMA modified natural rubber latex and / or styrene modified natural rubber latex are used. It is known that the use of these conventional modified natural rubber latex can improve the mechanical stability and enhance the surface strength of the coated surface. However, the problem that the cold seal adhesive strength of the cold seal adhesive may deteriorate due to heat, ultraviolet rays, or the like with time or during printing has not been solved.

Therefore, a cold seal adhesive that 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 The current situation is that it has not been obtained yet. In the present specification, the heat-resistant, UV-resistant, and ozone-resistant properties of the cold seal adhesive are described as being difficult to deteriorate by heat, UV, and ozone. Also called ozone.

[0016]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the problem is that the conventional cold seal adhesives using the conventional natural rubber latex have the following problems. The problem that the cold seal adhesive strength is deteriorated by heat, light, oxygen, ozone, etc. is alleviated, preferably substantially eliminated, and further,
Good blocking resistance, cold seal adhesion, and printability (related to offset printing, gravure printing, printing with non-impact printer, etc.),
It is an object of the present invention to provide a cold seal adhesive having high overall performance, which can easily adjust these properties appropriately. In addition, such a cold seal adhesive is applied to provide an adhesive site having a layer of adhesive formed thereon. In particular, it is to provide an information carrier having such an adhesion site.

[0017]

Means for Solving the Problems As a result of various studies on the resin used as an adhesive component of a cold seal adhesive, the present inventor has found that, as will be described in detail below, a conventional natural rubber-based latex is used in place of the natural rubber-based 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 a 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 new cold seal adhesive, which comprises a modified natural rubber latex obtained by graft-polymerizing an acrylic ester compound onto a natural rubber latex, to obtain a whole adhesive. A cold seal adhesive comprising 20 to 70% by weight of the composition. Further, according to another aspect of the present invention, there is provided an adhesive site coated with the cold seal adhesive according to the present invention to form a layer of the adhesive. According to another aspect of the present invention, there is provided a confidential postcard having the above-mentioned adhesive site.

[0019]

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

In the present specification, the term “water-based” cold seal adhesive means that the acrylic-modified natural rubber latex contained in the cold seal adhesive, and other resins and fine particle fillers described later that may 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. Throughout the present specification, parts by weight and% by weight are based on the part excluding the 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 in the total composition of the adhesive, based on the weight of the adhesive portion excluding the aqueous medium (100% by weight). Thus, it is an adhesive having a fluid form (for example, emulsion form, latex form) including a state in which a resin or the like is dissolved and / or dispersed in an aqueous medium.

In the present specification, the "aqueous medium" refers to general water such as distilled water and ion-exchanged water.
Water-soluble or water-dispersible organic solvents, monomers, oligomers, etc. may be contained within a range that does not adversely affect the properties of the cold seal adhesive of the present invention, and they are usually used in the production of the resin (A). It may contain an emulsifier or the like.

In the present invention, the resin (A): acrylic acid ester-modified natural rubber latex is an acrylic acid ester-modified natural rubber latex obtained by graft-polymerizing an acrylic acid ester compound on a natural rubber latex. Here, the acrylic ester compound is an ester compound obtained from a compound having acrylic acid and a hydroxyl group, and is particularly limited as long as it can obtain the cold seal adhesive aimed at by the present invention. is not.

Examples of acrylic acid ester compounds include 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. Acrylic acid alkyl esters having an alkyl group which may contain a branched chain; Acrylic acid cycloalkyl esters having a cycloalkyl group which may contain a substituent such as cyclohexyl acrylate; Hydroxyethyl acrylate and hydroxypropyl acrylate Acrylic acid alkyl esters having an alkyl group containing a hydroxyl group such as; and epoxide 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 acrylate alkyl esters having an alkyl group which may contain a branch, and further, in order to obtain sufficient polymerization stability in the graft polymerization reaction. In addition, the alkyl group which may contain a branch of acrylic acid alkyl ester has a carbon atom number of 1 to
It is preferably 10. Furthermore, as the acrylic acid ester compound, at least one selected from butyl acrylate, ethyl acrylate, and 2-ethylhexyl acrylate is particularly preferable. The above-mentioned acrylic acid ester compounds may be used alone or in combination and appropriately selected and used according to the properties of the intended cold seal adhesive.

The acrylic acid ester compounds also include acrylic acid amides such as acrylic acid amide and acrylic acid methylolamide, and the acrylic acid amides can be used alone or in combination.

The acrylic acid ester compound is graft-polymerized to the natural rubber latex to give the resin (A), with 0.1 to 20 parts by weight of the acrylic acid ester compound per 100 parts by weight of the natural rubber latex. Is preferably graft-polymerized with a natural rubber latex, more preferably 0.5-10 parts by weight of an acrylic acid ester compound is graft-polymerized, and 1-5 parts by weight of an acrylic acid ester compound is graft-polymerized. Is particularly preferable.

In addition to the above-mentioned acrylic acid ester compound, the natural rubber latex is preferably further polymerized with another polymerizable monomer. Here, the "other polymerizable monomer" is a compound that can be graft-polymerized to the above-mentioned natural rubber latex, generally a compound containing a functional group having an ethylenic double bond, For example, methacrylic acid alkyl esters such as methyl methacrylate, styrene, and acrylonitrile can be exemplified, and methacrylic acid alkyl esters are preferable.

The above-mentioned other polymerizable monomers may be used alone or in combination and appropriately selected depending on the characteristics of the intended cold seal adhesive. To the natural rubber latex, in addition to the above acrylic ester compound,
When another polymerizable monomer is polymerized, 1 to 50 parts by weight of the total amount of the acrylic acid ester compound and the other polymerizable monomer is 100 parts by weight of the natural rubber latex per 100 parts by weight of the natural rubber latex. Is preferably graft polymerized, and more preferably 3 to 30 parts by weight is graft polymerized. The acrylic ester compound and the other polymerizable monomer are preferably graft-polymerized to the natural rubber latex at the same time, but either one 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". The adhesive 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 aimed at by the present invention can be obtained, the modified natural rubber latex and / or styrene-modified natural rubber latex described above which has been conventionally used for cold seal adhesives can be used. Rubber latex is also included in the "natural rubber latex" used for producing 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 the acrylic acid ester compound which is polymerized into the natural rubber latex, and other polymerizable monomers which are used if necessary. : The properties of acrylic ester-modified natural rubber latex can be adjusted. Therefore, the heat resistance, UV resistance and ozone resistance of the cold seal adhesive can be adjusted.
Mechanical stability, cold seal adhesion, etc. can be easily adjusted.

Resin (A): Acrylic acid ester-modified natural rubber latex is usually obtained by using a conventional method commonly used as a method for producing a modified natural rubber latex, optionally using a catalyst and the like. Compound,
Further, it can be obtained by graft-polymerizing another polymerizable monomer, which is used as necessary, to the natural rubber latex. Reaction time of polymerization reaction, reaction temperature, acrylic acid ester compound, type and concentration of other polymerizable monomer used as necessary, 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 desired resin (A) and the like.

The term "catalyst" as used herein means a compound capable of causing a graft polymerization reaction of an acrylic acid ester 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 can be exemplified, and in particular, t
-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, regarding the resin (A): acrylic ester modified natural rubber latex as described above, the swelling rate 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 film of a conventional natural rubber-based latex, and any method may be used. it can. As a method for 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 will be described in detail in Examples described later, the film before being immersed in toluene (2.5 cm × 2.5 cm × 2
mm) as a standard (1), and refers to the magnification of the weight of the film after being immersed 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, particularly preferably 10 times or less. The swelling rate of the resin (A) is usually 5 to 15.

The cold seal adhesive of the present invention comprises the resin (A): acrylic ester modified natural rubber latex in an amount of 20 to 70% by weight in the total composition of the adhesive, but 30 to 60% by weight. Preferably. Here, the "wt%" is based on the portion containing no aqueous medium, as described above. Needless to say, the acrylic 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 contain resin (B): polyolefin resin. Here, "resin (B): polyolefin resin"
With the purpose of imparting wear resistance, blocking resistance, and removability, the cold seal adhesive of the present invention is blended, and may be a commonly used polyolefin resin, which 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)" that is water-based refers to a polyolefin-based resin that can exist in an aqueous medium, and is a resin (B) dissolved and / or dispersed in an aqueous medium (for example, an emulsion). Form) resin (B).

As such a resin (B), for example, polyethylene, polypropylene, and halogenated polyolefin such as chlorinated polyethylene and chlorinated polypropylene are modified (for example, carboxyl group, sulfonic acid group, phosphoric acid group, A resin that can be present in an aqueous medium by modifying it with a hydroxyl group or a hydrophilic group such as an amino group, a resin that can be present in an aqueous medium by using an emulsifier or a water-soluble polymer, and an aqueous medium Examples of the above-mentioned resin dispersed in Resin (B)
In particular, an aqueous dispersion of polyethylene is particularly preferable. Such a resin (B) can be produced by a known method, but a commercially available resin can be used, and examples thereof include Chemipearl W308 (trade name) manufactured by Mitsui Chemicals, Inc.

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

Further, the average particle diameter of the resin (B): polyolefin resin is preferably 0.1 to 20 μm, and is 0.5.
It is particularly preferable that the thickness is -15 μm. Here, the "average particle diameter of the resin (B)" refers to the particle diameter measured by the Coulter counter method. The polyolefin resins may be used alone or in combination as the resin (B). When the cold seal adhesive of the present invention comprises the resin (B), 100% by weight of the whole adhesive is used.
As the resin, the resin (B) is preferably contained in an amount of 0 to 30% by weight, particularly preferably 3 to 25% by weight.

The cold seal adhesive of the present invention is a resin other than resin (C): resin (A) and (B), and has a Tg of −.
You may further comprise at least 1 sort (s) selected from resin which is 30 degreeC or more. In the present invention, “resin (C): a resin other than the resins (A) and (B), having a Tg of −
At least one selected from resins having a temperature of 30 ° C or higher "
Is to be 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 other than resins (A) and (B). In the above resin, the Tg of the resin is −30 ° C. or higher, and at least one of the resins generally used for cold seal adhesives may be used. 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 "resin (C)" which becomes an aqueous system means a resin (C) existing in an aqueous medium, and a resin (C) in a state of being dissolved in the aqueous medium and / or a state of being dispersed (for example, The resin (C) in the form of emulsion or latex).

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

Examples of the "synthetic rubber resin" include styrene-butadiene copolymer (SBR), acrylonitrile-butadiene copolymer (NBR), and copolymer of acrylic acid esters and butadiene (MBR). it can. Examples of the “water-soluble polymer” include 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 one can be used. For example, as a synthetic rubber resin, Nipol manufactured by Nippon Zeon Co., Ltd.
Examples include LX416 (trade name) and Nipol SX1706 (trade name) manufactured by Nippon Zeon Co., Ltd. as the vinyl-based resin.

The Tg of the resin (C) is -30 ° C or higher, preferably -20 ° C or higher. Where resin (C)
The Tg of refers to the temperature described below, which is measured using a differential scanning calorimeter (DSC). The heat capacity of the resin (C) is measured using DSC to obtain a DSC curve. A straight line obtained by extending the low temperature side baseline of the stepwise change part based on the glass transition of the DSC curve to the high temperature side and a DSC drawn at a point where the slope of the DSC curve of the stepwise change part based on the glass transition is maximum. The temperature at the intersection with the tangent of the curve is Tg of the resin (C).

The resin (C) is preferably in the form of an emulsion, but it 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 contains the resin (C), the total amount of the adhesive is 100% by weight, and preferably 0 to 80% by weight of the resin (C),
It is particularly preferable to contain the resin (C) in an amount of 1 to 60% by weight.

The cold seal adhesive of the present invention may further comprise a particulate filler. The term "fine particle filler" as used herein means a fine particle filler usually used in cold seal adhesives, and examples thereof include silica gel, hollow silica, mica, calcium carbonate, kaolin, talc, diatomaceous earth, urea resin, and styrene beads. , Clay, grain starch, modified starch, and the like. Further, the fine particle filler is usually a particle, and the size thereof is not particularly limited as long as the performance targeted by the present invention is exhibited. These fine particle 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. You can

In the present invention, various additives can be added to the cold seal adhesive. The term "additive" as used herein refers to an additive that is usually used in a cold seal adhesive if necessary, and examples thereof include a lubricant, a printability improver, an antioxidant, an ultraviolet absorber, a radical scavenger, a conductive agent, and a fluorescent agent. Examples thereof include paints, coloring dyes, stabilizers, defoamers, antifungal agents, antibacterial agents, thickeners, and moisturizers.

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

The cold seal adhesive of the present invention is suitable as an adhesive for adhering a base sheet by applying pressure. The present invention further provides an adhesive site in which the cold seal adhesive described above is applied to a substrate sheet and dried to form a layer of adhesive. "Adhesion site" in the present specification
Here, the cold seal adhesive is applied and dried to form a layer of the adhesive, but it is a portion which is not yet bonded by applying pressure.

In one embodiment of the invention, a cold seal adhesive is applied to the surface of the substrate sheet to be printed and dried to form a layer of adhesive, after which information is printed on the surface to be printed. A part of the printed surface is bent so that the other part is in contact with each other, and the two layers of the bent adhesive are overlapped so as to be in contact with each other to provide an adhesive portion for pressing the two together.

In another embodiment of the invention, a cold seal adhesive is applied to the surface of the substrate sheet to be printed and dried to form a layer of adhesive and after printing the information on the surface to be printed. , The printed surface is coated with cold seal adhesive and dried so that the adhesive layer on both surfaces is in contact with the other surface on which the adhesive layer has been formed, and both are integrated. Provide an adhesive site for crimping.

Here, the "base sheet" is as described above. Further, "another surface on which a 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. It may be any other coated surface (usually the surface of the substrate sheet), for example such a surface may be printed prior to coating or an adhesive formed by coating. May be printed on top of the layers. Specifically, it refers to a surface that has been subjected to coating → printing, printing → coating, or only coating.

In the present specification, "coating" can be used without limitation as long as it is a coating method which has been conventionally used as a method for coating a cold seal adhesive. For example, a roll coater, a bar coater, a blade coater, an air knife coater, a rod blade coater, a gravure roll coater, etc. can be illustrated. Further, "coating" also includes the method used to apply the cold seal adhesive, eg,
Coating and spraying can also be used.

The term "drying" can be used without particular limitation as long as it is a conventionally used drying method for drying the cold seal adhesive, for example, natural drying, warm air. Examples thereof include drying and high frequency drying.

Further, "compression bonding" means that two surfaces on which an adhesive agent layer is formed by applying an adhesive agent and drying are brought into contact with each other in the same manner as the treatment conventionally used for cold sealing. It means that the two surfaces are bonded together by applying pressure and heat if necessary. Therefore, "crimping" means
It also means to apply pressure to the bonding site of the above-mentioned base sheet to bond them together.

Further, the present invention provides the above-mentioned bonding site which is bonded by applying pressure. Therefore, the above-mentioned bonded sites bonded together are also included in the present invention. The cold seal adhesive of the present invention can be used by using a method similar to the conventionally used cold seal adhesive, and such a method can be used to provide an adhesive site on the base sheet. Therefore, the present invention provides 20 to 70% by weight of the total adhesive.
Resin (A): Since a cold seal adhesive containing an acrylic acid ester-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 adhesive site that is substantially removed and that also exhibits excellent performance in terms of adhesion and blocking resistance.

Furthermore, an information carrier having such an adhesive site is provided. Particularly preferred forms of such information carriers are 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, the pressure bonding conditions for the information carrier, etc.
It is appropriately selected according to the intended information carrier (including any that requires the releasable or material-breaking property of the cold seal adhesive).

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

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

When the acrylic acid ester compound is graft-polymerized onto the natural rubber latex, the acrylic acid ester compound is added to the ethylenic double bond existing in the chain of the natural rubber, whereby the acrylic acid ester compound is converted into the natural rubber latex. It is thought to give a cross-linking structure between the chains. Therefore, it is considered that the number of ethylenic double bonds in the natural rubber decreases and the molecular chain becomes more difficult to move due to the formation of the cross-linking structure between the chains of the natural rubber. As a result, in the resin (A): acrylic acid ester-modified natural rubber latex, the ethylenic double bond, which causes deterioration of the natural rubber latex due to heat, UV, ozone, etc., is converted into a single bond to chemically react. It is considered that it is more stabilized physically and also physically more stabilized by imparting a crosslinked structure to the chain of natural rubber.

On the other hand, when the conventionally used monomers such as methyl methacrylate and styrene are graft-polymerized on the natural rubber latex, a polymer chain of natural rubber such as the above-mentioned acrylic ester compound is obtained. Methyl methacrylate and styrene may be addition-polymerized to the existing double bond, but it is considered that many of them are addition-polymerized between methyl methacrylate and styrene. 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, such as sea islands. Therefore, the mechanical stability of the conventional modified natural rubber latex was improved by graft-polymerizing methyl methacrylate and styrene onto the natural rubber latex because the physical stability of polymethyl methacrylate and polystyrene itself This is because the rubber latex was stabilized, and it is considered that the chemical stability of the natural rubber latex itself was not necessarily improved.

The fact that the chemical structure of the resin (A) is different from that of the natural rubber latex and the conventional modified rubber latex can be understood by examining the swelling ratio of each. The swelling ratio is considered to correspond to the crosslink density of each polymer chain, and the smaller the value, the more crosslinked the polymer chains are and the more difficult it is to move. According to the study by the present inventor, the swelling ratios of both the natural rubber latex and the conventional modified natural rubber latex are usually about 40 times, whereas the swelling ratio of the resin (A) is less than 40 times. . Therefore, while the natural rubber latex and the conventional modified natural rubber latex have the same degree of difficulty in moving the polymer chains,
The polymeric chains of resin (A) are believed to be more immobile than those. The difficulty in moving the polymer chain of the resin (A) is that the acrylic ester compound is addition-polymerized to the ethylenic double bond existing in the natural rubber chain, and the acrylic ester compound becomes the natural rubber chain. It is considered to be expressed by providing a cross-linking structure between the two.

Further, since the swelling ratio of the conventional modified natural rubber latex is similar to that of the natural rubber latex itself as described above, even if methyl methacrylate and styrene are graft-polymerized with the natural rubber latex, the natural rubber latex is The chain itself hardly changes its movement, and therefore, it is considered that the molecular structure itself of the natural rubber polymer does not change significantly. As a result, it is considered that methyl methacrylate and styrene are substantially polymerized with each other.

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

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

[0066]

EXAMPLES The present invention will be specifically described in detail below with reference to Examples and Comparative Examples, but these Examples are merely 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 stated, the parts containing no aqueous medium are used as the standard for parts by weight and% by weight.

Example 1 Production of Cold Seal Adhesive In a three-necked flask equipped with a stirrer, a thermometer and a reflux condenser,
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 polyoxyethylenealkylphenylsulfate 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, heated to 40 ° C., and then 0.4 parts by weight of tetraethylpentamine as a reducing agent was added to the mixture over 30 minutes to obtain the acrylic ester-modified natural product of Example 1. A rubber latex was obtained.

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

To 100 parts by weight of the acrylic ester-modified natural rubber latex of Example 1 was added 100 parts by weight of particulate filler (consisting of amorphous silica, starch and calcium carbonate), and 15 parts by weight of auxiliary agents. Thus, the cold seal adhesive of Example 1 was obtained. Therefore, the cold seal adhesive of Example 1 comprises 46.5% by weight of the acrylic ester modified rubber latex of Example 1.

Evaluation of Cold Seal Adhesive Preparation of Coating Sheet Using a high quality paper of 130 g / m ² as a base sheet, one side of this high quality paper is coated so that the coating amount after drying is 10 g / m ² . The cold-seal adhesive of Example 1 was applied and dried to obtain a coated sheet (hereinafter also referred to as "coated sheet of Example 1") on which an adhesive layer was formed.

Evaluation of Cold Seal Adhesiveness After the coated sheet of Example 1 was pressure bonded, the adhesive strength at the time of peeling (cold seal adhesive strength) was measured to evaluate the cold seal adhesiveness. The coated sheet of Example 1 was folded back in two so that the layers of the adhesive were overlapped with each other, and pressure-bonded using a mail sealer for pressure-bonding while changing the gap between the rollers in various ways. This pressure-bonded coated sheet 3
After leaving for 0 minutes, a T-type peel test was performed using a tensile tester at a pulling speed of 300 mm / min to measure the force required for peeling (cold seal adhesive force). 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 heated in an oven at 105 ° C. for 30 days.
The heat treatment was performed by holding it for a minute. Then 2
The coated sheet that had been aged for 4 hours was folded back in two so that the adhesive layers were overlapped, and was crimped with a gap between rollers of 220 μm using a crimping mail sealer. After leaving the pressure-bonded coated sheet for 30 minutes, a T-type peel test was performed at a pulling speed of 300 mm / min using a tensile tester to measure the force required for peeling. The cold seal adhesion of coated sheets that have not been heat treated is 10
The holding ratio of the cold seal adhesive strength of the coated sheet after the heat treatment when 0% was determined. The results are shown in Table 1.

Evaluation of UV resistance U of 15 W was applied to the adhesive coated surface of the coated sheet of Example 1.
By irradiating UV with a V lamp for 2 hours,
UV irradiation treatment was performed. Then, the coated sheet cured for 24 hours was folded back in two so that the layers of the adhesive were overlapped, and pressure-bonded with a gap between rollers of 220 μm using a pressure-sensitive mail sealer. After leaving the pressure-bonded coated sheet for 30 minutes, 300 mm /
A T-type peel test was performed at a pulling speed of minutes to measure the force required for peeling. The retention rate of the cold seal adhesive force of the coated sheet after the heat treatment was calculated when the cold seal adhesive force of the coated sheet that was not subjected to the UV irradiation treatment was 100%. The results are shown in Table 1.

Example 2 Example 1 was repeated except that 1 part by weight of butyl 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. A cold seal adhesive of Example 2 was obtained using a method similar to that described in 1.
Using a method similar to that 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 instead of 5 parts by weight of butyl acrylate and 5 parts by weight of methyl methacrylate. A cold seal adhesive of Example 3 was obtained using a method similar to that described in 1.
Using a method similar to that described in Example 1, Example 3
Of cold seal adhesives were evaluated. The results are shown in Table 1.

Comparative Example 1 Similar to the method described in Example 1 except that 25 parts by weight of methyl methacrylate was used in place of 5 parts by weight of butyl acrylate and 5 parts by weight of methyl methacrylate. The method was used to obtain the cold seal adhesive of Comparative Example 1. The cold seal adhesive of Comparative Example 1 was evaluated using a method similar to that described in Example 1. The results are shown in Table 1.

[0077]

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

Regarding the cold seal adhesive strength, from the values measured by changing the gap between the rollers, both of the cold seal adhesives of Examples and Comparative Examples had practically no problems. Regarding the heat resistance and UV resistance, it is understood that the cold seal adhesive retention 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 with the case of using a 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,
(For gravure printing, printing by a non-impact printer, etc.) is good, and a layer of an adhesive having high overall performance is formed in which these characteristics can be easily adjusted appropriately. Furthermore, an adhesive site on which such a layer of adhesive is formed is provided, in particular an information carrier having such an adhesive site is provided.

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Claims (8)

(57) [Claims] 1. A modified natural rubber latex obtained by graft-polymerizing an acrylic acid ester compound into a natural rubber latex, which is 0.1 to 2 per 100 parts by weight of the natural rubber latex.
Graft-polymerized 0 parts by weight of the acrylic ester compound.
A cold seal adhesive comprising the modified natural rubber latex obtained by 20 to 70% by weight, wherein the modified natural rubber latex has a swelling ratio of a film formed therefrom of 20 times or less. Agent. 2. The cold seal adhesive according to claim 1 , wherein the acrylic ester compound is at least one selected from alkyl acrylates having an alkyl group having 1 to 10 carbon atoms. Wherein the acrylic acid ester compound, butyl acrylate, ethyl acrylate, and cold seal adhesive according to claim 1 or 2 is at least one selected from 2-ethylhexyl acrylate. 4. A cold seal adhesive according to any one of claims 1 to 3, the polyolefin resin comprises further. 5. An adhesive site on which the cold seal adhesive according to any one of claims 1 to 4 is applied to form an adhesive layer. 6. A surface of a substrate sheet to be printed is coated with a cold seal adhesive and dried to form a layer of the adhesive, information is printed on the surface to be printed, and then the printed surface is printed. The bonding part according to claim 5 , wherein the part and the other part are bent so that they are in contact with each other, and the two layers of the adhesive that are bent are overlapped so as to be in contact with each other, and both are pressure-bonded together. 7. A base sheet is coated with a cold seal adhesive on the surface to be printed and dried to form a layer of the adhesive, information is printed on the surface to be printed, and then the printed surface is printed. Claim: A method for applying a cold seal adhesive and drying the adhesive to form another adhesive layer on the other surface so that the adhesive layers on both surfaces are in contact with each other and crimping them together. The adhesion site according to item 5 . 8. A confidential postcard having the adhesion site according to claim 6 or 7 .