JPH0788499B2 - Base paper adhesive for heat-sensitive stencil printing - Google Patents

Description

The present invention relates to a heat-sensitive stencil sheet adhesive which is easy to apply and can provide an adhesive layer having excellent heat sensitivity (perforability) and printing durability. Conventionally, in thermal stencil printing, (a) a thermoplastic resin film, for example, a vinylidene chloride-vinyl chloride copolymer, a copolymer film containing propylene or the like as a main component, a polyester film,
(B) a porous support, for example, thin paper, cloth, or non-woven fabric in which natural fibers or chemical fibers are singly or intertwined, and (c) an adhesive, for example, a vinyl acetate adhesive, an acrylic adhesive,
A heat-sensitive stencil printing base paper consisting of (a), (b) and (c), which is laminated using a rubber adhesive, is used.

And as the property of the adhesive used at this time,
(I) The coating process can be performed quickly. The properties of the adhesive layer after production of the base paper include (ii) when the base paper and the original are irradiated with an infrared lamp or a flashlight to form a perforated image, they are melted simultaneously with the thermoplastic resin film (so-called , Excellent in heat sensitivity), (ii
i) After perforating the base paper, the adhesive layer is not attacked by the material in the printing ink during repeated printing, and the adhesive strength is excellent (so-called printing durability is excellent). is there.

However, since the adhesive used when manufacturing the base paper for heat-sensitive stencil printing is conventionally mixed with a large amount of a solvent and a dispersant, it takes a lot of time (about 10 to 20 m / min) for the coating process,
The production efficiency was significantly hindered. Moreover, since the solvent used at this time is volatile, it is likely to cause a fire, air pollution, etc. Therefore, a large amount of equipment was required to recover the solvent.

In addition, the vinyl acetate adhesive, which is most widely used because of its easy handling, does not have sufficient adhesive strength. For example, when printing the same image for 3 days, the heat-sensitive stencil printing base paper is left on the printing machine overnight in contact with the printing ink, during which the adhesive layer is gradually attacked by the printing ink. When left alone for one night and then printed, the image becomes unclear and the original number of printed sheets cannot be achieved.

Therefore, as a result of diligent efforts to solve the above-mentioned drawbacks, the inventors of the present invention use a urethane prepolymer capable of limiting the flow initiation temperature after reaction curing for a urethane adhesive that has been conventionally difficult to use. The coating processing speed is 5 to 10 times faster than that of the conventional product, and the cured adhesive layer has a good perforation property due to ordinary heat-sensitive heat treatment, for example, heat-sensitive plate making using an infrared lamp or flash. The present invention has been completed based on the finding that a heat-sensitive stencil printing base paper that exhibits heat sensitivity), is not attacked by the solvent in the printing ink, has excellent adhesive strength, and can be printed for two days or more is obtained. Of.

That is, the present invention is an adhesive for producing a base paper for heat-sensitive stencil printing by laminating a thermoplastic resin film and a porous support, wherein the adhesive is the thermoplastic resin film and the porous support. 0.3 when applied with
~ 2.5 g / m ² , average molecular weight of 400 with diisocyanate ~
Equivalent ratio of 2,000 polyether diols NCO / OH = 1.5-
The main component of the urethane prepolymer obtained by reacting in the range of 2.0, the flow start temperature after curing is 150
It is a base paper adhesive for heat-sensitive stencil printing (hereinafter abbreviated as base paper adhesive), which has a temperature of up to 260 ° C.

Examples of the diisocyanate used in the present invention include hexamethylene diisocyanate (HMDI), 2,4-diisocyanate-1-methylcyclohexane, 2,6-diisocyanate-1-methylcyclohexane, diisocyanate cyclobutane, tetramethylene diisocyanate, O-, and m. -, And p-xylylene diisocyanate (XDI), dicyclohexylmethane diisocyanate, dimethyldicyclohexylmethane diisocyanate, hexahydrometaxylidene diisocyanate (HX
DI), and resinous or cycloaliphatic diisocyanates such as lysine diisocyanate alkyl esters (wherein the alkyl portion of the alkyl ester preferably has 1 to 6 carbon atoms): toluylene-2,4-diisocyanate ( TDI), toluylene-2,6-diisocyanate,
Diphenylmethane-4,4'-diisocyanate (MDI),
3-methyldiphenylmethane-4,4'-diisocyanate, m- and p-phenylene diisocyanate, chlorophenylene-2,4-diisocyanate, naphthalene 1,5
Aromatic diisocyanates such as diisocyanates, diphenyl-4,4'-diisocyanates 3,3'-dimethyldiphenyl, -1,3,5-triisopropylbenzene-2,4-diisocyanate and diphenyl ether diisocyanates: and mixtures thereof To be

Examples of the polyether diol used in the present invention include polyethylene glycol (PEG), polypropylene glycol (PPG), polyoxyethylene-polypropylene block copolymer, polytetramethylene glycol, polytetramethylethylene glycol, polybutadiene glycol, hydrogenated. Examples thereof include polybutadiene glycol, bisphenol A base diol, and acrylic polyether diol.

The polyether diol has an average molecular weight (number average molecular weight, the same applies hereinafter) of 400 to 2,000, preferably 800 to 1,000. When it is less than 400, the viscosity becomes too high when applied as an adhesive and handling is difficult, which is not preferable. or,
It is not preferable because the pot life becomes short and handling on the coating machine becomes difficult.

If the average molecular weight exceeds 2,000, the piercing property and printing durability of the adhesive layer after production of the base paper are deteriorated, which is not preferable.

Diisocyanate and polyether diol are equivalent in NC
A urethane prepolymer reacted in the range of O / OH = 1.5 to 2.0 is used. When NCO / OH <1.5, the flow start temperature of the urethane prepolymer after curing tends to be lower than 150 ° C,
Adhesion is reduced, which is not preferable.

Further, the viscosity of the urethane prepolymer becomes high and the workability is poor.

When NCO / OH> 2.0, isocyanate monomer remains,
Not good for hygiene.

The base paper adhesive of the present invention is reacted with an isocyanate group in the adhesive and a chain extender, for example, water, glycol, diamine, etc., and cured as a chain molecule, so that the end of the prepolymer is an NCO group. It is necessary to have at least two NCO groups in one molecule of the prepolymer.

The base paper adhesive of the present invention may be manufactured by a stepwise manufacturing method or a batch charging method. For example, in the batch charging method, diisocyanate and polyether diol are charged all at once at a ratio of NCO / OH = 1.5 to 2.0,
Further, if necessary, a solvent and a catalyst (for example, phosphoric acid, dibutyltin dilaurate, etc.) are charged at the same time, and they are reacted with stirring in a closed container or under a nitrogen stream at 50 to 120 ° C. to terminate the urethanization reaction. Then, if necessary, the solvent is distilled off to obtain a reaction product (prepolymer). In the stepwise production method, diisocyanate is pre-reacted so that a predetermined equivalent amount of isocyanate groups remain, and then a predetermined proportion of polyether diol is charged so as to react stoichiometrically. Should be terminated.

The prepolymer thus obtained can be cured by adding light (steam), glycol, diamine or the like, or by applying light energy such as ultraviolet rays, but the method is not particularly limited.

The flow starting temperature after the reaction curing of the base paper adhesive of the present invention is 15
It is in the range of 0 to 260 ° C (preferably 150 to 240 ° C). 260
If the temperature exceeds ℃, the holes may not be completely opened (perforated) due to heat during plate making, and a good image may not be obtained.

The flow start temperature can be adjusted by adding a flow start temperature lowering agent to the prepolymer.
As the flow start temperature lowering agent, a thermoplastic resin that does not contribute to the urethane reaction, such as wax, rosin, rosin ester, petroleum resin, a thermoplastic urethane branching reaction inhibitor (for example, butadiene sulfone, paratoluene sulfonic acid, phosphoric acid esters, Borate esters) and the like can be added.

The coating amount of the base paper adhesive of the present invention is suitably in the range of 0.3 to 2.5 g / m ² , and preferably 0.5 to 1.5 g / m ² . If the coating amount is less than 0.3 g / m ² , the adhesive strength will be weak and the film and the porous support will be easily peeled off. ^{On the other hand} , if it exceeds 2.5 g / m ² , even if the adhesive layer becomes thin due to pressure bonding, the amount of the adhesive itself is too large to perform heat-sensitive perforation sufficiently and a good image cannot be obtained. A preferable coating amount is 0.5 to 1.5 g / m ² .

The viscosity at 25 ° C. of the base paper adhesive (prepolymer) of the present invention is preferably 10,000 cps or more, more preferably 50,000 cps or more from the viewpoint of productivity. After bonding the thermoplastic resin film and the porous support, it usually takes 24 to 48 hours at room temperature to completely cure, but if the viscosity of the adhesive is too low, the adhesive will be cured before it is cured. In some cases, the adhesive may be transferred to the film surface of the wound base paper, or the adhesive may flow downward when the wound roll is stood and stored, resulting in unevenness of the adhesive layer. The base paper adhesive of the present invention does not usually need to contain a solvent, but if necessary, a small amount may be added.

The thermoplastic resin film to be adhered to the porous support may be a thermoplastic resin film (particularly highly oriented or stretched film) that can be used for heat-sensitive stencil printing, and examples thereof include polyester, polyvinylidene chloride, and vinylidene chloride-vinyl chloride. Films such as the copolymers and the copolymers containing propylene as a main component are used, and polyester (RET) -based films and polyvinylidene chloride-based films are suitable.

Further, the porous support may be a porous support that does not substantially have perforation properties when heated and allows ink to pass through during printing, such as Manila hemp, thin paper or nonwoven fabric of polyester fiber, polyester fiber, A preferable example is a silk screen gauze.

Examples and comparative examples will be described below. The parts are parts by weight.

Example 1 47.5 parts of diphenylmethane-4,4'-diisocyanate and an average molecular weight of 1,000 so that NCO / OH = 1.9 in equivalent ratio.
(100 parts of polypropylene glycol) and 0.2 part of phosphoric acid as a catalyst were charged into a reaction group and reacted at 70 ° C. for 4 hours in a nitrogen atmosphere to obtain a urethane prepolymer as a base paper adhesive for heat-sensitive stencil printing of the present invention. This base paper adhesive is 25 ℃
The viscosity was 80,000 cps and the flow initiation temperature after moisture curing was 208 ° C. In addition, the flow start temperature is 20kg with an advanced flow tester, orifice diameter 1.0mmφ, length
It is a value measured at 1.0 mm and a heating rate of 6 ° C./min (hereinafter,
The same measurement is performed for each example and comparative example).

The urethane prepolymer adhesive obtained in this way
The mixture was heated to 100 ° C. and supplied to the coating roller of a solventless laminator which was also heated to 100 ° C., and the polyester film (thickness 2 μm) and the porous support (8.5 g / m ² Manila hemp paper) were attached to each other. The pressure at the time of bonding (pressure between rollers) was 5 kg / cm ² , and the amount of adhesive applied was 0.8 g / m ² . In this step, generation of decomposition products or vaporized products was not observed at all.

Using the heat-sensitive stencil printing base paper prepared as described above, a heat-sensitive copying machine (lithograph FX7200, manufactured by Riso Kagaku Kogyo Co., Ltd.) was used to make a plate at the position of scale 3, and the printing machine (lithograph AP7200, Ridekaku Kagaku Kogyo) Printing was performed with a product manufactured by KK, and a good printed image was obtained.

The following measurements were also carried out, and the results are shown in Table 1.

(B) Number of printable sheets A thermal type copying machine (lithograph FX7200) was used to attach ink to the heat-sensitive stencil printing plate made at the position of scale 3 and allowed to stand for 12 hours before printing (lithograph AP7200 as a printing machine). Is used) and the horizontal line with a width of 0.15 mm is 0.
Indicates the number of prints when the size becomes 3mm.

(B) Perforation rate (%) The ratio of the perforated portion of the solid printing portion of the heat-sensitive stencil printing paper at the position of the scale 3 by means of a heat-sensitive copying machine (lithograph FX7200).

Example 2 25 parts of diphenylmethane-4,4'-diisocyanate (MDI) so as to have an equivalent ratio of NCO / OH = 1.9 and 64 parts of polypropylene glycol having an average molecular weight of 2,000 so that the polyetherdiol has an average molecular weight of 1470. And 11 parts of bisphenol A propylene oxide adduct having an average molecular weight of 575 (product of Asahi Denka Co., Ltd .; ADEKA POLYETHER BPX-33) were charged in a container and reacted at 70 ° C. for 4 hours under a nitrogen atmosphere to obtain a heat-sensitive stencil of the present invention. A urethane prepolymer as an adhesive for printing base paper was obtained.

This base paper adhesive has a viscosity at 25 ° C of 130,000 cps,
The flow initiation temperature after moisture curing was 225 ° C.

After that, a heat-sensitive stencil printing base paper was produced in the same manner as in Example 1, and plate making and printing were carried out in the same manner as in Example 1, and a good printed matter was obtained because it was a base paper having excellent heat sensitivity.

Example 3 Toluylene-2.4- so that NCO / OH = 1.6 in equivalent ratio
Diisocyanate (TDI) 12.5 parts, diphenylmethane-
4,4'-diisocyanate (MDI) 12.5 parts, average molecular weight,
37.5 parts of 1,000 polyethylene glycol and 0.1 part of phosphoric acid were charged into a container and reacted under a nitrogen atmosphere at 70 ° C for 6 hours,
A urethane prepolymer as an adhesive for the heat-sensitive stencil printing base paper of the present invention was obtained. This base paper adhesive has a viscosity of 14 at 25 ° C.
It was 0,000 cps, and the flow initiation temperature after moisture curing was 182 ° C.

After that, a heat-sensitive stencil printing base paper was manufactured in the same manner as in Example 1, and plate making and printing were carried out in the same manner as in Example 1. As a result, the base paper was excellent in heat sensitivity and a good printed matter was obtained.

Example 4 23.1 parts of hexamethyldiisocyanate, 76.3 parts of polytetramethylene ether glycol having an average molecular weight of 1,000, and dibutyltin dilaurate 0.01 as a catalyst were charged in a container in a nitrogen atmosphere so that NCO / OH = 1.8 in an equivalent ratio. Then, the reaction was carried out at 80 ° C. for 6 hours to obtain a urethane prepolymer as an adhesive for the base paper for heat-sensitive stencil printing of the present invention.

This base paper adhesive had a viscosity at 25 ° C. of 60,000 cps and a flow initiation temperature after moisture curing of 196 ° C.

After that, a heat-sensitive stencil printing base paper was produced in the same manner as in Example 1, and plate making and printing were carried out in the same manner as in Example 1, and a good printed matter was obtained because it was a base paper having excellent heat sensitivity.

Example 5 Toluylene-2.4 was used so that the equivalent ratio would be NCO / OH = 1.55.
-Diisocyanate (TDI) 60 parts, diphenylmethane-
70 parts of 4,4'-diisocyanate (MDI), average molecular weight 700
280 parts of polypropylene glycol and 100 parts of rosin ester (Arakawa Chemical Co., Ltd., ester gum HD) are charged into a reactor and reacted under a nitrogen atmosphere at 80 ° C. for 3 hours to prepare a urethane prepolymer as a main component of the present invention. A base paper adhesive for heat-sensitive stencil printing was obtained.

This base paper adhesive has a viscosity at 25 ° C of 340,000 cps,
The flow initiation temperature after moisture curing was 185 ° C.

After that, a heat-sensitive stencil printing base paper was produced in the same manner as in Example 1, and plate making and printing were carried out in the same manner as in Example 1, and a good printed matter was obtained because it was a base paper having excellent heat sensitivity and adhesiveness. It was

Comparative Example 1 Diphenylmethane was adjusted so that the equivalent ratio would be NCO / OH = 1.3.
32.5 parts of 4,4'-diisocyanate and 100 parts of polypropylene glycol having an average molecular weight of 1,000 were charged in a reactor and reacted at 70 ° C for 3 hours in a nitrogen atmosphere to obtain a urethane prepolymer adhesive.

This adhesive had a viscosity at 25 ° C. of 28,000 cps and a flow initiation temperature after moisture curing of 142 ° C.

Thereafter, a heat-sensitive stencil printing base paper was produced in the same manner as in Example 1,
When plate making and printing were carried out in the same manner as in Example 1, the base paper was excellent in heat sensitivity, but the adhesive layer was easily attacked by the printing ink, and the number of printing sheets was only 20.

Comparative Example 2 4 parts of diphenylmethane-4,4'-diisocyanate and 360 parts of polypropylene glycol having an average molecular weight of 360 were placed in a reactor so that NCO / OH = 1.8 in an equivalent ratio, and the reaction was carried out at 70 ° C for 3 hours in a nitrogen atmosphere. Then, a urethane prepolymer adhesive was obtained.

The adhesive had a viscosity at 25 ° C. of 210,000 cps and a flow initiation temperature after moisture curing of 236 ° C.

Hereinafter, a heat sensitive stencil printing base paper was produced in the same manner as in Example 1,
When plate making and printing were carried out in the same manner as in Example 1, the base paper was excellent in heat sensitivity, but the adhesive layer was easily attacked by printing ink, and the number of printing sheets was only 300.

Comparative Example 3 475 parts of diphenylmethane-4,4′-diisocyanate and 2500 parts of polypropylene glycol having an average molecular weight of 2500 were charged into a reactor so that the equivalent ratio would be NCO / OH = 1.9, and the reaction was carried out at 80 ° C. for 4 hours in a nitrogen atmosphere. Then, a urethane prepolymer adhesive was obtained.

This adhesive had a viscosity at 25 ° C. of 45,000 cps and a flow initiation temperature of 180 ° C. after moisture curing.

Hereinafter, a heat sensitive stencil printing base paper was produced in the same manner as in Example 1,
When an attempt was made to carry out plate making and printing in the same manner as in Example 1, the heat sensitive part was not sufficiently perforated because the adhesive layer of the base paper was poor in heat sensitivity, and printing was impossible.

Comparative Example 4 15 parts of a polyvinyl acetate copolymer having an average degree of polymerization of 600 and 2 parts of a phenol resin were dissolved in 83 parts of methanol to obtain a base paper adhesive.

Using this adhesive, the porous paper used in Example 1 and the polyester film were laminated by a wet lamination method to produce a heat sensitive stencil printing base paper, and plate making and printing were carried out in the same manner as in Example 1. It took a lot of time to manufacture.

As can be understood from the results shown in Table 1 above, the coating process using the adhesive for heat-sensitive stencil printing of the present invention can be carried out by various methods, but sometimes it can be applied by using a solventless laminator. In addition, the coating processing speed is 5 to 10 times faster (100 to 200 m / min) than that of the conventional product, showing high productivity.

Further, the adhesive layer of the coating processed portion is excellent in adhesive strength and solvent resistance. Therefore, the heat-sensitive stencil printing base paper using the heat-sensitive stencil printing base paper adhesive of the present invention has a perforation property even in plate making and printing ( It is excellent in heat sensitivity) and resolution, and is excellent in printing durability without being affected by printing ink even when printing for 2 days or more.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Sukegawa 2-20-15 Shimbashi, Minato-ku, Tokyo Inside Ideal Science Co., Ltd. (56) Reference JP-A-58-52378 (JP, A) JP-A-SHO 53-21236 (JP, A) Keiji Iwata, "Polyurethane Resin," pages 248-251, November 30, 1969, published by Nikkan Kogyo Shinbunsha

Claims (1)

[Claims] 1. An adhesive for producing a heat-sensitive stencil printing base paper by bonding a thermoplastic resin film and a porous support to each other, wherein the adhesive is a combination of the thermoplastic resin film and the porous support. Applying amount of 0.3 to 2.5 g / m ²
The main component is urethane prepolymer obtained by reacting diisocyanate and polyether diol having an average molecular weight of 400 to 2,000 in an equivalent ratio of NCO / OH = 1.5 to 2.0. A base paper adhesive for heat-sensitive stencil printing, which has a temperature of 150 to 260 ° C.