JPS6377984A - Pressure-sensitive adhesive sheet - Google Patents

Abstract

PURPOSE:To obtain the title sheet which has excellent adhesiveness, is free from blocking during storage and when treated under a high-temperature object, and is to be pressed against the same sheet with the adhesive layers of these sheets being opposed to each other, by forming an adhesive layer comprising a pressure-sensitive adhesive, a pigment, and a tackifier on a base sheet. CONSTITUTION:A composition is obtained by mixing 100pts.wt. (dry weight) pressure-sensitive adhesive (a) (e.g., a self-adhesive natural rubber resin), 400-1,000pts.wt., preferably 600-800pts.wt., pigment (b) comprising inorganic or organic particles that have neither pressure-sensitive nor heat-sensitive adhesiveness (e.g., a silica of an average particle diameter of 8mum or less), and 50-300pts.wt., preferably 80-20pts.wt., tackifier (c) (e.g., a rosin resin). This composition is applied to a base sheet comprising, e.g., a woodfree paper consisting mainly of cellulose fibers or a synthetic paper to a coat of 5-20mum thick to form an adhesive layer on the base sheet, thus giving the title sheet. This sheet is to be pressed against the same sheet with the adhesive layers of these sheets being opposed to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a pressure-sensitive adhesive sheet. , In more detail, it has good adhesive strength when the adhesive layers provided on the sheet are faced to each other and pressed with strong pressure. 1. The adhesive layer and the adhesive are not coated. 2. If the adhesive layers are in contact with each other or are pressed with a light load, 3. If the adhesive layer is in contact with a high-temperature body, there will be no adhesion. The present invention relates to a pressure-sensitive adhesive sheet that does not develop tackiness (blocking properties).

(B) Prior Art Various natural and synthetic adhesive resins having pressure-sensitive adhesive properties are known. These resins are printed or coated on a film or paper serving as a support and used as pressure-sensitive adhesive tapes, and are commercialized as, for example, adhesive tapes, cellophane tapes, and the like. These adhesives have various types of adhesive resin, support, and adhesive strength depending on the purpose of use, and are commonly used on a daily basis. In addition, recently, for business forms, sheets are printed or coated with pressure-sensitive or heat-sensitive adhesives, which are stacked so that each adhesive layer faces each other, and then bonded by applying strong pressure or heating. There is an increasing demand for pressure-sensitive adhesive sheets and heat-sensitive adhesive sheets that can be processed into slips, forms, envelopes, postcards, etc., and they are also introduced in literature publications.

(C) Problems to be Solved by the Invention These pressure-sensitive adhesive sheets and heat-sensitive adhesive sheets are subjected to various printing, cutting, packaging, and bending processes during the manufacturing and processing process.

In addition, the use of electrophotographic printers for printing has recently increased, and in this process, it is essential to fix the toner using a high-temperature body, so thermoplastic adhesives are practically used. It's impossible.

In other words, electrophotographic printers are equipped with a heating element to fix the toner, and the sheet is inevitably exposed to high heat, and when the adhesive layer on the sheet comes into contact with the heating element, it may jam due to blocking. (A paper jam)
It is clear that such troubles are unavoidable when heat-sealing type adhesives are used.

However, even pressure-sensitive adhesives exhibit thermoplasticity to some extent depending on the type of resin, and essentially, when exposed to high heat, the phenomenon of fusion cannot be avoided. In addition, even if no heat is applied, blocking may occur if the adhesive layers are in contact with each other under a light load, or if the adhesive and the support sheet are stored for a long time in contact with each other.
This may become an unfavorable phenomenon in handling operations in the next process.

To address these problems, Japanese Patent Laid-Open No. 61-34552,
1-35279, 61-345501 6l-345
In the 5L 6'l-34552 specification, by adding an inorganic or organic 1a pigment (so-called anti-blocking agent) that has no thermoplasticity and no pressure-sensitive adhesive properties, it is possible to prevent paper from blocking each other and to melt against high-temperature bodies. It is stated that it prevents staining and improves running performance during printing.

However, these pigments inherently reduce adhesive strength, and the amounts added as described in the above-mentioned publications are insufficient to completely eliminate blocking.

In addition, JP-A No. 61-34553 describes the addition of silicone-based paraffin wax-based lubricants, metal soap-based lubricants, and mold release agents as materials to prevent blocking and thermal adhesion, but these also contain pigments. As in the previous case, this resulted in a considerable decrease in adhesive strength, and no matter what adhesive was used in combination, a satisfactory bonding point could not be found.

In view of the above problems, the present inventor aims to provide a pressure-sensitive adhesive sheet with good adhesive strength.

More specifically, (1) when the adhesive layer and the support sheet to which no adhesive is applied are facing each other and pressurized, (2) when the adhesive layers are in contact with each other or when pressurized with a light load. ,(
3) To provide a pressure-sensitive adhesive sheet that does not cause any odor blocking when the adhesive layer comes into contact with a high-temperature body.

(D> Means for solving the problem The present invention basically involves setting the addition and mixing ratio of the three types of adhesive, pigment, and tackifier that form the pressure-sensitive adhesive layer within a specific range. The present invention provides a pressure-sensitive adhesive sheet that exhibits sufficient adhesive strength when pressed and that does not cause any blocking even when exposed to any harsh conditions.

The adhesive used in the present invention can be used as long as it has pressure-sensitive adhesive properties, and preferred examples include natural rubber resin, acrylic resin, styrene-butadiene resin, and synthetic rubber resin. Particularly preferred examples include natural rubber-based resins that have excellent self-adhesive properties. These resins can be mixed as long as the adhesive strength is not reduced.

Pigment refers to inorganic or organic particles that do not exhibit pressure-sensitive or heat-sensitive adhesive properties. Specifically, silica, kaolin, calcium carbonate, titane oxide, aluminum hydroxide, zinc white, clay, talc, melamine particles, melamine resin particles,
Examples include benzoguanamine particles and starch particles, and particularly preferred examples include silica having an average particle diameter of 8 μm or less in consideration of dispersibility, antiblocking properties, printability, etc.

Various tackifiers are known, and one that is most compatible with the adhesive and pigment may be selected.

Specific examples of tackifiers include rosin resins and their derivatives, terpene resins, terpene phenol resins, C5 petroleum resins, C9 petroleum resins, styrene resins, alkylphenol resins, xylene resins, and chromalone indene resins. In the present invention, rosin resins are particularly preferred.

The mixing ratio of these components is 400 to 1,000 parts of pigment to 100 parts of adhesive (dry weight), preferably 60 parts of pigment.
By setting the amount of the tackifier in the range of 0 to 800 parts, and more preferably 80 to 200 parts, maximum adhesive strength was obtained and no blocking property occurred. If the amount of both pigment and tackifier added is outside this range, the balance between adhesive strength and blocking property will be lost, resulting in trouble.

The support for the pressure-sensitive adhesive sheet is not particularly limited, and high-quality paper mainly composed of cellulose fibers and various synthetic papers can also be used.

The coating thickness of the pressure-sensitive adhesive ink is suitably in the range of 5 to 20 microns. Application and printing methods include air knife coating, blade knife coating, flexo printing,
Screen printing is mentioned as a preferred method. The composition may contain thickeners, dispersants, antifoaming agents, preservatives,
It is also possible to add deterioration inhibitors and the like.

(E) Examples The present invention will be explained in more detail with reference to Examples.

All weights shown in Examples and Comparative Examples indicate parts by weight in a dry and dehydrated state.

Example 1 100 parts of Nisudyne #MS-32 (manufactured by Tsukisui Chemical Co., Ltd., natural rubber latex) was used as a pressure-sensitive adhesive, and Mizukasil P-832 (manufactured by Mizusawa Chemical Co., Ltd., synthetic silica, average particle diameter 3!II) was used as a pigment. 'n) 700 parts, 5 as tackifier
N-TACK (manufactured by Sannopco, rosin-based tackifier)
140 parts were mixed and the nonvolatile content concentration was adjusted to 45%.

Furthermore, the viscosity was reduced to 25% using commercially available carboxymethyl cellulose.
00 cps (B type viscosity 25° C. 60 rf) l) to obtain a pressure-sensitive adhesive water-based ink.

This ink was applied to a 3 mm width on all sides of a piece of high quality paper with a basis weight of 150 g/'rIt, and flexo printing was carried out to a thickness of 8 μm to obtain 1 q of pressure-sensitive adhesive sheet for making envelopes. This sheet was folded so that the adhesive layers faced each other, and then pressed using a rigid calendar roll at a pressure of 100 kg/cm, and an envelope was instantly obtained.

Example 2 The same Nisdyne #MS-3 as in Example 1 was used as a pressure sensitive adhesive.
2100 parts, as a pigment, 800 parts of Jilton M-42 (manufactured by Mizusawa Chemical, semi-synthetic silica, average particle size 7.0 pn)
and Rika Hercilus (Tai Sei D-1) as a tackifier.
200 parts of 88 (rosin-based tackifier) were mixed to adjust the nonvolatile content to 50%. Using commercially available carboxymethyl cellulose, the viscosity was adjusted to 2200 cps to obtain a water-based pressure-sensitive adhesive ink.

This ink was processed into general high-quality paper in the same manner as in Example 1,
When subjected to pressure treatment, the adhesive force was sufficient to cause paper layer destruction, and there was no blocking at all on the adhesive-coated surface before processing.

Example 3 100 parts of acrylic emulsion AE-944 (manufactured by Japan Synthetic Rubber Co., Ltd., acrylic emulsion) as an adhesive, 500 parts of talc for papermaking as a pigment, and Cellosol #B-523 (manufactured by Middle East Yushi Co., Ltd., terpene phenol resin) as a tackifier. Emulsion) 90 parts added, non-volatile content 52%
The viscosity was further adjusted to 1800 CI) using commercially available carboxymethyl cellulose to obtain a pressure-sensitive adhesive ink.

When this ink was processed into high-quality paper in the same manner as in Example 1, a pressure-sensitive adhesive sheet with good adhesion was obtained.

Example 4 Styrene-butadiene latex L-'1 as adhesive
432 (manufactured by Asahi Kasei Industries, Ltd., SBR latex), 200 parts of Eposta-3U-6 (manufactured by Nippon Shokubai, benzoguanamine particles) as a pigment, and CKE- as a tackifier.
2370 (Showa Kobunshi phenolic resin emulsion)
250 parts was added to adjust the nonvolatile content to 32%, Example 1
A pressure-sensitive adhesive sheet was obtained by applying air knife coating to the entire wire surface of the same high-quality paper to a coating thickness of 15 μm.

This sheet is cut into a size twice the size of a normal government postcard, folded in half and subjected to rigid calendar roll pressure 300'J.
When pressurized at a pressure of /cm, the entire coated surface was instantly and completely adhered and could be used as a postcard.

Comparative Example 1 Pressure-sensitive adhesive ink 19 was prepared in the same manner as in Example 1 except that the amount of pigment P-832 added was changed to 50 parts, and a pressure-sensitive adhesive sheet was obtained in the same manner.

Comparative Example 2 Pressure-sensitive adhesive ink was prepared in the same manner as in Example 1 except that the amount of pigment P-832 added was 1050 parts.
A pressure-sensitive adhesive sheet was further obtained in the same manner.

Comparative Example 3 A pressure-sensitive adhesive ink was obtained in Example 1 without adding 5N-TACK, and a pressure-sensitive adhesive sheet was obtained in the same manner.

Comparative Example 4 A pressure-sensitive adhesive ink was obtained in the same manner as in Example 1 except that the amount of 5N-TACK added was 350 parts.
Further, a pressure-sensitive adhesive sheet 1- was obtained in the same manner.

Comparative Example 5 A pressure-sensitive adhesive ink was obtained in the same manner as in Example 1, except that wheat starch (average particle size 18IR) was used instead of Mizukasil P-832, and a pressure-sensitive adhesive ink was obtained in the same manner as in Example 1. An adhesive sheet was obtained.

Various properties of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were evaluated according to the following test methods.

1. Adhesiveness The adhesive force when pressed with a rigid calendar roll was evaluated in two levels: pressure force of 100 Kg/cm and 300 Kg/crn.

Judgment criteria Q: ○ Paper layer destruction occurs.

Δ　Does not cause paper layer destruction but adheres well are doing.

× means almost no adhesion 2, light load blocking property Overlap the sheets so that the coated surfaces are facing each other, and apply 5 sheets from above.
Criteria for evaluating blocking properties after applying a light load of K3/ci and leaving at room temperature for 72 hours: ○ No blocking at all △ Some blocking The blocking property was evaluated when the sheet was brought into contact with the sheet and sandwiched from above and below with a household iron heated to 200'C for 10 seconds.

Judgment criteria are 2. The pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples, which are the same as the light load blocking properties, and the copying machine direction, were cut into 8-4 sizes, and then cut into 8-4 size sheets and placed on a PPc copier 4370 manufactured by Fuji Xerox Co., Ltd.
Evaluate runnability when treated with type.

Judgment Criterion 20: Printable without problems X　Print quality, runnability, etc. are not possible The above evaluation results are summarized in Table 1.

(F) Effect of the invention As is clear from the examples, the mixing ratio of the adhesive, pigment, and tackifier, which are the components of the adhesive layer on the pressure-sensitive adhesive sheet, is By setting the adhesive strength within this range, it is possible to obtain a pressure-sensitive adhesive sheet that has excellent adhesive strength and does not cause any blocking during storage or processing under a high-temperature body. This means that the pressure-sensitive adhesive sheet according to the present invention will not cause any trouble under any processing conditions encountered during actual use, and can be very useful industrially.

Procedural principal 11l official document (spontaneous) 1. Indication of the case 1985 Patent Application No. 223401, Name of the invention Pressure-sensitive adhesive sheet 3, Person making the amendment Relationship with the case Special applicant address Marunouchi, Chiyoda-ku, Tokyo 3-4-2 Mitsubishi Paper Mills Co., Ltd. Patent Department δ (600) 2111 4. Subject of amendment Section ``Detailed Description of the Invention'' in Mei III (1) Specification;
Insert "3. Detailed Description of the Invention" between the fourth line from the bottom and the third line from the bottom of the first page.

(2) Same as above, from the last line of page 3 to the first line of page 4, "it could be like this" was corrected to "it could be like this."

(3) Same, page 5, line 11 “The inventor is” The present invention shall be amended to ``the present invention.''

Claims (1)

[Claims] 1) A pressure-sensitive adhesive sheet in which adhesive layers provided on the sheet are bonded by facing each other and applying pressure, the composition of the adhesive layer basically being 100 parts of the pressure-sensitive adhesive. A pressure-sensitive adhesive sheet comprising 400 to 1000 parts of a pigment and 50 to 300 parts of a tackifier based on (dry weight). 2) The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive is a self-adhesive natural rubber adhesive. 3) The pressure-sensitive adhesive sheet according to claim 1, wherein the pigment is silica having an average particle diameter of 8 μm or less. 4) The pressure-sensitive adhesive sheet according to claim 1, wherein the tackifier is a rosin resin.