JPH07278509A - Production of rubber-based tacky tape - Google Patents

Abstract

PURPOSE:To obtain a tape having a high holding power and tack in a simple step by mixing a specific rubber with a tackifying resin, coating a substrate with the resultant hot-melt tacky agent and then irradiating the formed tacky agent layer with electron rays. CONSTITUTION:This method for producing a rubber-based tacky tape is to add and mix (B) preferably 20-200 pts.wt. tackifying resin composed of a rosin- based resin, a-pinene, a terpene phenol resin, etc., and, as necessary, (C) preferably 20-200 pts.wt. softening agent composed of a process oil such as preferably a naphthenic or an aromatic process oil with (A) 10.0 pts.wt. preferably natural rubber having 100000-500000 weight-average molecular weight, coat a substrate such as paper, a cloth or a plastic film with the resultant rubber-based hot-melt tacky agent and then preferably irradiate the formed tacky agent layer with electron rays in an atmosphere of an inert gas. Furthermore, the irradiation dose is a quantity so as to provide 25-65wt.% get fraction of the tacky agent layer after the irradiation and is usually 5-150Mrad.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rubber adhesive tape using a hot melt adhesive.

[0002]

2. Description of the Related Art Rubber-based pressure-sensitive adhesives have been widely used for pressure-sensitive pressure-sensitive adhesive tapes since they have excellent flexibility, elasticity and adhesiveness. The production method is generally a method in which rubber, tackifying resin, etc. are dissolved in an organic solvent such as toluene at a solid content concentration of several 10%, the solution is applied to a substrate, and then the solvent is dried by heating. Target. However, in the manufacturing process by this solvent method, it takes time to dissolve rubber etc. in the solvent, a long dryer and a large amount of heat are required for drying the solvent, and not only is it costly to recover the solvent. However, there is a risk of ignition depending on the working environment, and it is not desirable from the viewpoint of air pollution and hygiene.

Therefore, in recent years, a method for producing a pressure-sensitive adhesive tape using a hot-melt pressure-sensitive adhesive and not using a solvent has been investigated. Since the hot-melt pressure-sensitive adhesive is melted by heating and applied to the substrate, it is necessary to suppress the molecular weight of the polymer material, which is the main component of the pressure-sensitive adhesive, to be low. However, as a result, there is a drawback that the cohesive force of the pressure-sensitive adhesive is lowered and the holding power after sticking the tape is poor.

As a measure for increasing the holding power, an attempt has been made to increase the cohesive force by applying a pressure-sensitive adhesive and then crosslinking a polymer material. That is, in JP-B-56-14573, 0.03 to 7 mol% of maleic anhydride or a derivative thereof is added to low molecular weight polyisoprene having a molecular weight of 1,000 to 90,000, and a metal crosslinking agent is added thereto. And mixing the tackifying resin at a temperature of 80 ° C. or higher,
Hot-melt pressure-sensitive adhesives that undergo crosslinking treatment have been reported. However, when a pressure-sensitive adhesive tape is produced using this pressure-sensitive adhesive, the process is complicated because a modification step of isoprene is required, and a crosslinking reaction partially occurs before coating,
There is a drawback that the difference in viscosity leads to variations in tape thickness after coating.

Japanese Patent Publication No. 4-56072 discloses that
An isoprene-based oligomer having functional groups capable of reacting with an isocyanate group in the amount of 1.5 to 2 per molecule and having the functional groups only at the ends of the molecular chain, and a polyfunctional isocyanate compound. A cross-linking pressure-sensitive adhesive containing a tackifying resin as a component has been reported. However, even in the case of this pressure-sensitive adhesive, there is a problem that the modification process of the isoprene-based oligomer is complicated, strict control of the pot life until coating is required, and the management of water content in the pressure-sensitive adhesive is also complicated. is there.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made for the purpose of producing a rubber-based pressure-sensitive adhesive tape having high holding power and adhesiveness by a simple manufacturing process. Is.

[0007]

In order to achieve the above object, 1 of the present invention comprises adding and mixing a tackifier resin to rubber, and 2 of the present invention relates to rubber, a tackifier and a softening agent. A rubber-based hot melt adhesive obtained by adding and mixing agents is applied to a substrate, and the adhesive layer is irradiated with an electron beam.

The rubber used in the present invention constitutes the main component of the pressure-sensitive adhesive and is a natural rubber or a synthetic rubber such as styrene-butadiene rubber, butadiene rubber, chloroprene rubber or nitrile rubber. In particular, natural rubber exhibits excellent performance. Natural rubber is, for example, RSS-No. 1 to 4, SMR.
-5L, SMR-20, CV-60 and the like are preferable, but not limited thereto. And since most of them have high molecular weight, mechanically lower the molecular weight with a mixing roll, Banbury kneader, kneader, etc.
Improves initial tack and coatability.

The average molecular weight of the rubber is important for the work of applying the adhesive and the adhesive properties of the tape, and the weight average molecular weight must be 100,000 to 500,000. The weight average molecular weight here is based on polystyrene conversion by gel permeation chromatography (GPC). If the average molecular weight is low, sufficient cohesive force cannot be obtained,
If it is too high, the viscosity of the pressure-sensitive adhesive also becomes high, which makes coating work difficult.

The softening agent used in the present invention lowers the viscosity of the rubber hot melt adhesive to improve the coating property. For example, petroleum softening agents such as process oil and extender oil, tall oil, etc. Vegetable oil-based softener,
Examples thereof include synthetic plasticizers such as dibasic acid ester plasticizers. Process oils are particularly preferable, and naphthene type, aromatic type and other known process oils can be used alone or in combination. The average amount of the softening agent is 100,000.
20 to 2 per 100 parts by weight of rubber of 500,000
It is preferable to add 100 parts by weight.

The tackifying resin plays a role of increasing initial tack and adhesion, and is a polymer of terpenes such as rosin resin, pentaerythritol ester compound of rosin resin, α-pinene and β-pinene. Or
Terpene resins containing these copolymers, terpene modified products such as terpene phenol resins, petroleum resins such as aromatic hydrocarbon resins and aliphatic hydrocarbon resins, and hydrides thereof can be used. In addition, phenol resins such as coumarone indene resin and alkylphenol acetylene resin and known resins can be used alone or in combination. The amount of tackifying resin is 20 to 200 with respect to 100 parts by weight of rubber.
It is preferred to add parts by weight. If the mixing amount is small, a good initial adhesive force cannot be obtained, and if it is too large, the desired cohesive force cannot be obtained.

The rubber-based pressure-sensitive adhesive composition used in the present invention contains, in addition to rubber, a tackifying resin or a softening agent, if necessary, a filler such as calcium carbonate or clay, a pigment and an antiaging agent. Etc. can be added.

As a device for mixing the above composition, a Banbury kneader, a kneader, a twin-screw kneading extruder is used. When it is necessary to lower the molecular weight of the rubber, it is possible to lower the molecular weight of the rubber and then mix the tackifying resin, the softening agent, and other additives. May be. The temperature at the time of mixing can be uniform at or above the softening point of the tackifying resin, but on the other hand, it is appropriate to keep the temperature below 200 ° C. in consideration of the deterioration of the rubber.

The base material of the pressure-sensitive adhesive tape is selected according to its application such as paper, cloth, plastic film and foam sheet. The thickness of the base material is also determined depending on its use and purpose. The back surface of the substrate may be treated with a release agent.

When applying the pressure-sensitive adhesive to the substrate, the temperature of the pressure-sensitive adhesive is raised to reduce the viscosity, and the pressure-sensitive adhesive is applied to a predetermined thickness with a coating machine such as a die coater, a knife coater or a curtain coater. Die coaters are preferred. The pressure-sensitive adhesive temperature during coating is preferably in the range of 140 to 200 ° C, and most preferably 160 to 180 ° C. If the temperature is 140 ° C or lower, the viscosity of the pressure-sensitive adhesive may be high and coating may be difficult. If the temperature exceeds 200 ° C, the rubber-based pressure-sensitive adhesive is likely to deteriorate, which is not desirable.

The viscosity of the pressure-sensitive adhesive suitable for coating is 10 to 50 ×
10 ³ CPS (capillary viscometer, die; diameter 1 mm
Length 10mm, temperature 160 ℃, shear rate 1000s ^-1 )
In the range of 15 to 40 × 10 ³ C, coating is easier
It is PS. If the pressure-sensitive adhesive viscosity exceeds 50 × 10 ³ CPS, coating becomes impossible. The thickness of the pressure-sensitive adhesive layer is determined by the application and purpose of the pressure-sensitive adhesive tape.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape thus obtained is irradiated with an electron beam. The electron beam irradiation device is a scanning electron beam irradiation device or a non-scanning electron beam irradiation device, and is appropriately selected depending on the processing conditions. The electron beam irradiation dose is such that the gel fraction of the adhesive layer after being irradiated with the electron beam is 2
Adjust to be 5 to 65% by weight. Generally, in the irradiation dose range of 5 to 150 megarads (Mrad), the adhesive tape after electron beam irradiation exhibits appropriate cohesive force and high adhesive force. The electron beam irradiation atmosphere may be under air, but under inert gas is preferable in order to prevent deterioration of the rubber-based pressure-sensitive adhesive.

Typical practical examples of the method for producing the rubber-based adhesive tape of the present invention include cellophane tape, craft tape,
Examples include cloth tape, Japanese paper tape, plastic tape, and adhesive labels.

[0019]

In the present invention, a rubber-based hot melt adhesive having excellent adhesive strength is used, and crosslinking between rubber molecules is performed by irradiation with an electron beam after coating to form an adhesive layer having high cohesive strength. can do.

[0020]

EXAMPLES Next, the method for producing the pressure-sensitive adhesive tape of the present invention will be described with reference to Examples. (Example 1) Natural rubber (RSS-No. 1) was masticated with a mixing roll at 80 ° C to adjust the weight average molecular weight to 400,000. Next, 100 parts by weight of this masticated rubber was mixed with petroleum resin ("Quinton A-1" manufactured by Nippon Zeon Co., Ltd.).
00 ") and 40 parts by weight of process oil (" KT-40 "manufactured by Idemitsu Kosan Co., Ltd.) were added and mixed well using a kneader to obtain a natural rubber hot melt adhesive composition.

The pressure-sensitive adhesive composition is heated to about 170 ° C.,
A polyethylene terephthalate film having a thickness of about 38 μm was coated on one surface with a knife coater to a thickness of about 40 μm. Then, the surface of the pressure-sensitive adhesive layer was irradiated with an electron beam with a dose of 40 Mrad under an atmosphere of air using a scanning electron beam irradiation device to prepare a pressure-sensitive adhesive tape.

(Example 2) Natural rubber (RSS-No. 1)
Was masticated at 80 ° C. with a mixing roll to adjust the weight average molecular weight to 200,000. Next, to 100 parts by weight of this masticated rubber, 120 parts by weight of a petroleum resin (“Quinton A-100” manufactured by Nippon Zeon Co., Ltd.) was added, and well mixed using a kneader to prepare a natural rubber hot melt adhesive composition. Got

The pressure-sensitive adhesive composition is heated to about 170 ° C.,
A polyethylene terephthalate film having a thickness of about 38 μm was coated on one surface with a knife coater to a thickness of about 40 μm. Then, the surface of the pressure-sensitive adhesive layer was irradiated with an electron beam with a dose of 30 Mrad under an atmosphere of air using a scanning electron beam irradiation device to prepare a pressure-sensitive adhesive tape.

(Example 3) Natural rubber (RSS-No. 1)
Was masticated with a mixing roll at 80 ° C. and adjusted so that the weight average molecular weight was 400,000. Next, to 100 parts by weight of this masticated rubber, 100 parts by weight of petroleum resin (“Quinton A-100” manufactured by Nippon Zeon Co., Ltd.) and 80 parts by weight of process oil (“KT-40” manufactured by Idemitsu Kosan Co., Ltd.) were added,
The mixture was thoroughly mixed using a kneader to obtain a natural rubber-based hot melt adhesive composition. Thereafter, the application of the pressure-sensitive adhesive and the electron beam irradiation were carried out in the same manner as in Example 1 to prepare a pressure-sensitive adhesive tape.

(Example 4) Natural rubber (RSS-No. 1)
Was masticated at 80 ° C. with a mixing roll to adjust the weight average molecular weight to 200,000. Next, 100 parts by weight of a petroleum resin (“Quinton A-100” manufactured by Nippon Zeon Co., Ltd.) was added to 100 parts by weight of this masticated rubber, and they were well mixed using a kneader to prepare a natural rubber hot melt adhesive composition. Got

The pressure-sensitive adhesive composition is heated to about 170 ° C.,
A polyethylene terephthalate film having a thickness of about 38 μm was coated on one surface with a knife coater to a thickness of about 40 μm. Then, the surface of the pressure-sensitive adhesive layer was irradiated with an electron beam with a dose of 20 Mrad under an atmosphere of air using a scanning electron beam irradiation device to prepare a pressure-sensitive adhesive tape.

(Comparative Example 1) 100 parts by weight of natural rubber (weight average molecular weight of about 1,000,000) which is not masticated at all, 100 parts by weight of petroleum resin ("Quinton A-100" manufactured by Nippon Zeon Co., Ltd.), process oil (Idemitsu Kosan Co., Ltd.) (Made by "KT-40")
80 parts by weight of toluene was mixed with 100 parts by weight of toluene, dissolved by stirring, and the solution was dried by a vacuum dryer to remove the toluene to obtain an adhesive composition. This composition was heated to be applied to one side of a polyethylene terephthalate film having a thickness of about 38 μm with a knife coater, but the viscosity was 70%.
The coating was too high at × 10 ³ CPS to be applied.

(Comparative Example 2) An adhesive tape was prepared in the same manner as in Example 3 except that no electron beam was applied.

(Comparative Example 3) An adhesive tape was prepared in the same manner as in Example 4, except that no electron beam was applied.

Comparative Example 4 An adhesive tape was prepared in the same manner as in Example 3 except that no process oil was used, but the viscosity of the adhesive composition was 60 × 10 ³ C.
The PS was too high to apply.

(Evaluation) The evaluation was made with four items: the viscosity of the pressure-sensitive adhesive composition before electron beam irradiation, the initial tack value and holding power (cohesive force) of the pressure-sensitive adhesive tape, and the gel fraction of the pressure-sensitive adhesive after electron beam irradiation. went. The viscosity of the pressure-sensitive adhesive composition was measured with a capillary viscometer. The measurement was performed using a die having a diameter of 1 mm and a length of 10 mm under the conditions of a temperature of 160 ° C. and a shear rate of 1000 s ⁻¹ .

The initial tack value of the adhesive tape is JIS-Z.
It was measured by the tack test method (ball rolling method) of 0237. The holding power of the adhesive tape was determined according to JIS-Z0237 by the holding power test method, and the tape was cut into a size of 25 mm × 150 mm to give a test piece, which was attached to a stainless steel plate of SUS-27 by 25 mm × 25 mm, 40 A load of 2 kg was applied to one end of the test piece at a temperature of ° C, and the time required for the test piece to shift and drop was measured.

The gel fraction of the pressure-sensitive adhesive was measured by peeling the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape from the substrate, immersing it in tetrahydrofuran, and measuring the weight of the insoluble rubber component remaining after standing for 24 hours (after drying). Then, the weight ratio (% by weight) to the original rubber compounded was calculated.

The results are shown in Table 1. As can be seen from the evaluation results, in each of the examples, the pressure-sensitive adhesive composition was 30
The viscosity is about 40 × 10 ³ CPS, which is easy to apply.
The gel fractions of the pressure-sensitive adhesives after electron beam irradiation were all 35 to 38% in the examples, which shows that crosslinking of rubber molecules proceeded by electron beam irradiation. In Comparative Example, since the electron beam irradiation was not performed, the gel fraction was 0%, and it can be seen that the crosslinking of rubber molecules did not occur. As a result, in each of the examples, the holding power is 2-3 hours, but in the comparative example, it is extremely low, 0-0.1 hours.

[0035]

[Table 1]

[0036]

As described above and as can be seen from the evaluation of the examples, according to the method for producing a rubber-based pressure-sensitive adhesive tape of the present invention,
Since no solvent is used, the process is simplified, and since no crosslinking agent or the like is added, there is no concern about pot life or storability, and coatability is good. Since the cross-linking of rubber molecules is carried out by electron beam irradiation after coating on the substrate, the adhesive tape obtained has excellent holding power.

Claims (2)

[Claims] 1. A weight average molecular weight of 100,000 to 50.
A method for producing a rubber-based pressure-sensitive adhesive tape, which comprises applying a rubber-based hot-melt pressure-sensitive adhesive obtained by mixing 50,000 rubbers and a tackifying resin to a substrate and irradiating the pressure-sensitive adhesive layer with an electron beam. . 2. The rubber-based hot melt pressure-sensitive adhesive is a mixture of a rubber having a weight average molecular weight of 100,000 to 500,000, a tackifying resin and a softening agent. Manufacturing method of the rubber-based adhesive tape of.