JPH09235533A - Acrylic tacky agent composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition excellent in low-temperature adhesion characteristics, especially tack, adhesiveness to a synthetic resin foam and cohesive power, mainly comprising an alkyl (meth)acrylate, having specific physical properties. SOLUTION: This composition mainly comprises an alkyl (meth)acrylate [preferably a 4-12C alkyl (meth)acrylate such as ethyl (meth)acrylate] and is made to have <=-10 deg.C maximum value in a temperature range of -50 to 100 deg.C when logarithmic damping factors measured by a pendulum type viscoelastic measuring equipment at the temperatures are plotted against the temperatures. The objective composition is preferably cross-linked so as to maintain adhesion properties at a high temperature. The composition is prepared by subjecting a monomer mainly comprising an alkyl (meth)acrylate to solution polymerization to give an acrylic copolymer having 350,000-750,000 weight-average molecular weight and, if required, blending the copolymer with a tackifier resin to control adhesion characteristics and optionally adding various additives to the blend.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an acrylic pressure-sensitive adhesive composition.

[0002]

2. Description of the Related Art In recent years, acrylic pressure-sensitive adhesive compositions used for labels, pressure-sensitive adhesive tapes, double-sided pressure-sensitive adhesive tapes, etc. have adhesive properties such as tack, peel resistance and cohesive strength in consideration of their use environment. In addition, weather resistance, color tone, transparency, etc. are required. The use of this acrylic pressure-sensitive adhesive composition is widespread, and the properties required for it are becoming more sophisticated. This acrylic pressure-sensitive adhesive composition has tack in itself, and can be a pressure-sensitive adhesive without adding a tackifying resin, but the adhesiveness to polyethylene resin products and polypropylene resin products and the adhesiveness to metal products are poor. There's a problem.

An acrylic pressure-sensitive adhesive obtained by copolymerizing a carboxyl group-containing monomer with an acrylic monomer is used in order to improve adhesion to metal products.
The acrylic pressure-sensitive adhesive composition containing an increased amount of the carboxyl group-containing monomer has a practically unacceptable decrease in adhesion to polyethylene resin products and polypropylene resin products. Therefore, as a pressure-sensitive adhesive composition to be attached to a polyethylene resin product or a polypropylene resin product, an acrylic pressure-sensitive adhesive composition obtained by adding a tackifying resin to a copolymer obtained by copolymerizing an acrylic monomer and a carboxyl group-containing monomer. Things are being used.

However, although the acrylic pressure-sensitive adhesive composition containing this tackifying resin has improved adhesiveness to polyethylene resin products and polypropylene resin products at room temperature,
There is a problem that the adhesiveness at low temperatures, particularly the tack, is significantly reduced. As a method for solving the above problem, Japanese Patent Laid-Open No. Hei 3
As described in JP-A-281587, an acrylic pressure-sensitive adhesive composition in which a resin acid esterified product having a specific hydroxyl value is added as a tackifying resin is known.

[0005]

However, although the acrylic pressure-sensitive adhesive composition described in the above publication has improved adhesiveness at low temperatures, it has improved adhesiveness to synthetic resin foams such as polyurethane resin foam and polyethylene resin foam. And the cohesive force was not always satisfactory.
Therefore, an object of the present invention is to provide an acrylic pressure-sensitive adhesive composition having excellent adhesive properties at low temperature, particularly excellent tack, and excellent adhesiveness and cohesive force to synthetic resin foams such as polyurethane resin foam and polyethylene resin foam. It is to provide things.

[0006]

The present invention has been made in order to achieve the above-mentioned object, and is composed of an alkyl (meth) acrylate as a main component and at a temperature of -50 to + 100 ° C. The maximum value in the above temperature range when the logarithmic decrement measured by a viscoelasticity measuring device is plotted against temperature is −10 ° C. or less.

The alkyl group of the alkyl (meth) acrylate used in the present invention preferably has 2 to 14 carbon atoms,
More preferably, it is 4-12. Examples of the alkyl (meth) acrylate include ethyl acrylate and n-
Propyl (meth) acrylate, isopropyl (meth)
Acrylate, n-butyl (meth) acrylate, se
c-butyl (meth) acrylate, t-butyl (meth)
There are acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate and the like. And
These alkyl (meth) acrylates may be used alone or in combination of two or more.

In addition to the above-mentioned alkyl (meth) acrylate, a carboxyl group-containing vinyl monomer having a double bond, such as (meth) acrylic acid, itaconic acid, (anhydrous) maleic acid, (anhydrous) fumaric acid, if necessary. And (meth) acrylonitrile, N-vinylpyrrolidone, N-vinylcaprolactam, (meth) acryloylmorpholine, (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth)
High polar group-containing vinyl monomers such as acrylate and dimethylaminopropyl (meth) acrylamide, and copolymerizable vinyl monomers such as methyl (meth) acrylate, styrene and vinyl acetate may be used in combination. The amount of the vinyl monomer blended in the monomer containing the alkyl (meth) acrylate as a main component is 0.5 to 3
0% by weight is preferred. The reason is that if it is less than 0.5% by weight, it is difficult to obtain the cohesive force, and if it exceeds 30% by weight, the cohesive force becomes too high and it becomes difficult to obtain the adhesiveness to the uneven surface of the synthetic resin foam or the like.

The acrylic pressure-sensitive adhesive composition of the present invention is preferably cross-linked in the same manner as the conventional acrylic pressure-sensitive adhesive composition, in order to maintain the pressure-sensitive adhesive properties at high temperatures. As the crosslinking method at this time, an electron beam irradiation method, a thermal crosslinking method using a peroxide or the like, and as a commonly performed method, an isocyanate crosslinking agent, an epoxy crosslinking agent, a melamine crosslinking agent, an aziridine crosslinking agent, a metal There is a method of adding a chelating cross-linking agent or a cross-linking agent such as a polyfunctional monomer to cross-link. When cross-linking with the above-mentioned cross-linking agent, it is necessary to previously introduce a polar group serving as a cross-linking starting point into the copolymer. Specifically, in the case of adding an isocyanate cross-linking agent, 2-hydroxyethyl is used. A hydroxyl group-containing vinyl monomer such as (meth) acrylate or 3-hydroxypropyl (meth) acrylate is preferably copolymerized, and in the case of an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, a metal chelate-based crosslinking agent, etc. It is preferable that the above-mentioned carboxyl group-containing monomer is copolymerized.

The acrylic copolymer of the present invention can be prepared by adding a polymerization initiator to a monomer mixture consisting of the above acrylic monomer and vinyl monomer, and subjecting it to a polymerization method such as solution polymerization, bulk polymerization, suspension polymerization and photopolymerization. Although it can be obtained by polymerization, solution polymerization is preferable from the viewpoint that the heat of polymerization can be dispersed and the viscosity can be adjusted. Examples of the polymerization initiator used in the solution polymerization include thermal polymerization initiators such as azobisisobutyronitrile and benzoyl peroxide. The weight average molecular weight of the acrylic copolymer is preferably 200,000 to 1,500,000. More preferably, it is 350,000-750,000. If it is less than 200,000, it will be difficult to obtain the necessary cohesive force, and if it exceeds 1.5 million, the viscosity will be high and the productivity in the coating step will be poor. Further, a chain transfer agent may be appropriately added in order to control the molecular weight of the acrylic copolymer of the present invention, and examples thereof include lauryl mercaptan.

In the present invention, a tackifying resin may be mixed with the above acrylic copolymer, if necessary, to control its tackiness to an optimum range. As this tackifying resin, there are conventionally known tackifiers such as natural resin type rosin derivative type, terpene phenol type resin type, synthetic resin type aromatic petroleum resin type, coumarone indene resin type, phenol resin type and xylene resin type. Resin can be used. The acrylic pressure-sensitive adhesive composition of the present invention may optionally contain conventionally known various additives such as a plasticizer, a softening agent, a filler, a pigment, a dye and the like.

The acrylic pressure-sensitive adhesive composition of the present invention is measured by a pendulum type viscoelasticity measuring device. Then, when the measured logarithmic decrement was plotted against temperature, -50 to +
The maximum value in the range of 100 ° C is -10 ° C or less. A measuring method using the pendulum type viscoelasticity measuring device will be described with reference to FIG. In FIG. 1, A is a pendulum, and this pendulum A has the structure shown in (a). That is, a square frame is provided by attaching a U-shaped frame member 2 having a side length of 50 mm to both ends of a cylinder 1 having a diameter of 2 mm and a length of 50 mm, and a length of 153 mm from the center of the lower side 21 of the frame. The leg part 3 is provided. In the pendulum A, a magnet suction plate 4 having a length of 20 mm and a width of 10 mm was attached at a position 30 mm from the lower side 21 of the leg portion 3, and a stopper 5 having a length of 20 mm and a width of 55 mm was attached at a position 3 mm from the bottom. It is a thing.

Then, at a position of 80 mm between the magnet suction plate 4 and the stopper 5 of the leg portion 3 of the pendulum A, a brass load 6 of 9.15 g shown in (b) is slidably attached. The frequency of the pendulum A can be adjusted by moving the position of the load 6 up and down.
The weight of the pendulum A is 12.35 g, and the total weight including the load is 21.5.

Viscoelasticity is measured as follows using this cylindrical rigid pendulum type viscoelasticity measuring device. The acrylic pressure-sensitive adhesive composition having a thickness of 60 μm applied and dried on a release sheet is transferred to an aluminum test plate,
With the acrylic adhesive composition layer of the adhesive tape facing upwards, the base material and the test plate are attached with a double-sided adhesive tape, the adhesive layer is provided on the test plate, and this is placed on the cooling / heating block. After setting, the cylinder 1 is placed on the acrylic pressure-sensitive adhesive composition layer, the pendulum A is set, the magnetic attraction plate 4 is attracted by electromagnetic force to lift the leg portion 3, and then the electromagnetic force is removed. The pendulum A starts free vibration around the cylinder 1.

The outer peripheral surface of the cylinder 1 vibrates while rolling back and forth over the acrylic pressure-sensitive adhesive composition by a small distance due to the amplitude of the pendulum A. The rolling resistance between the outer peripheral surface of the cylinder and the adhesive layer when vibrating attenuates the amplitude. The damping rate of this oscillation is plotted against temperature. Sample temperature control is
It is performed in a cooling / heating block in which an aluminum test plate provided with an acrylic pressure-sensitive adhesive composition layer is set. That is, at low temperatures,
Liquid nitrogen is used as a coolant, and heater heating is used in a high temperature range to precisely control the temperature. Further, the vibration amplitude of the pendulum 4 is accurately measured using a non-contact type displacement gauge.

In the acrylic pressure-sensitive adhesive composition of the present invention, when the logarithmic decrement measured by this cylindrical rigid pendulum viscoelasticity measuring instrument is plotted against the temperature, the temperature at which the logarithmic decrement (Δ) becomes maximum is shown. It is -10 ° C or lower. The reason for this is that when the temperature at which the logarithmic decrement (Δ) becomes maximum exceeds −10 ° C., the adhesiveness to the uneven surface of the synthetic resin foam or the like deteriorates. The acrylic pressure-sensitive adhesive composition of the present invention may be used as a double-sided pressure-sensitive adhesive tape by molding it into a tape shape or a sheet shape, or the pressure-sensitive adhesive of the present invention may be layered on one or both sides of a tape-shaped or sheet-shaped base material. You may use it as an adhesive tape or an adhesive sheet provided in. The substrate used here is paper, non-woven fabric, plastic film such as polyester resin film or olefin resin film, or polyolefin resin foam, polyurethane resin foam, polychloroprene resin foam, soft polyvinyl chloride resin foam A tape-shaped or sheet-shaped synthetic resin foam such as acrylic resin foam can be used.

(Function) The acrylic pressure-sensitive adhesive composition of the present invention comprises an alkyl (meth) acrylate as a main component and has a logarithmic attenuation measured by a pendulum type viscoelasticity measuring device at each temperature of -50 to + 100 ° C. When the ratio is plotted against temperature, the maximum value in the above temperature range is -1
Since it is 0 ° C. or less, it is excellent in tack at low temperature and has excellent adhesive performance such as adhesiveness to a synthetic resin foam such as a polyurethane resin foam or a polyethylene resin foam.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

(Examples 1, 2, 3, 4, Comparative Examples 1, 2, 3) (Preparation of Acrylic Copolymer) In accordance with the composition shown in Table 1, n-butyl acrylate, 2-ethylhexyl acrylate, acrylic acid, 2 -Hydroxyethyl acrylate, vinyl acetate and lauryl mercaptan together with 80 parts by weight of ethyl acetate, stirrer, reflux condenser, thermometer,
The mixture was charged into a five-necked flask equipped with a dropping funnel and a nitrogen gas inlet, stirred and uniformly mixed, and then purged with nitrogen gas for about 30 minutes to remove oxygen existing in the monomer solution. Then, the air in the flask was replaced with nitrogen gas, the temperature was raised with stirring, the temperature was maintained at 70 ° C., and a solution prepared by dissolving 0.03 part by weight of benzoyl peroxide in 1 part by weight of ethyl acetate was added dropwise. After dropping with a funnel, polymerization was carried out at the same temperature for 10 hours to give A in Table 1.
Three types of acrylic copolymers shown in B and C were produced.

(Preparation of Acrylic Adhesive Composition) According to the formulation shown in Table 2, the acrylic copolymer and the tackifying resin are uniformly mixed while being diluted with toluene to a concentration of 45.
A toluene solution of a weight% acrylic pressure-sensitive adhesive composition was prepared.

(Preparation of Adhesive Tape) An ethyl acetate solution of a trimethylolpropane adduct of tolylene diisocyanate as a cross-linking agent in a toluene solution of the above acrylic adhesive composition (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate L55E"). (55% by weight of solid) was added to 1.5 parts by weight with respect to 100 parts by weight of the acrylic copolymer, and the mixture was mixed uniformly, and then, on one surface of the polyester film having a thickness of 38 μm, the thickness after drying was 60 μm. Coating so that
Then, it was dried at a temperature of 110 ° C. for 5 minutes to prepare an adhesive tape. Using the above-mentioned adhesive tape, the maximum temperature of the logarithmic decrement (△), tack,
The holding power and the adhesive power to the polyurethane resin foam were measured, and the results are shown in Table 3.

Measuring method 1. Maximum temperature of logarithmic decay rate (△) The polyester film side of the adhesive tape and the aluminum test plate are attached with the double-sided adhesive tape, the acrylic adhesive composition layer is provided on the upper surface, and this is set on the cooling / heating block. Then, from above, the support 1 of the pendulum A shown in FIG. 1 is placed so as to come into contact with the acrylic pressure-sensitive adhesive composition layer. After the magnetic attraction plate attached to the leg portion 3 is attracted and lifted by using an electric magnet, the pendulum A starts free vibration by cutting off electricity. The damping state of the vibration of this pendulum A and the temperature of the adhesive are measured, and the logarithmic damping rate (△)
Plot the relationship between temperature and temperature. Then, the temperature at which the logarithmic decay rate (Δ) reaches the maximum value is measured. The temperature of the sample is accurately controlled by using a cooling / heating block in which a test plate made of aluminum with an adhesive tape attached is set as liquid nitrogen in the low temperature region and using heater heating in the high temperature region.

2. Using a tack tack tape, according to ASTM D-2979 "Probe tack method", with a probe tack measuring machine,
Both the speed of contact with the surface of the adhesive tape and the speed of release are 10 mm
/ Sec, contact load 100 gf / cm ² , contact time 1 second 0
The pull-off resistance at 25 ° C and 23 ° C is measured and used as a tack.

3. Holding power According to JIS Z0237, a 25 mm x 25 mm adhesive tape is attached to a stainless steel plate made of SUS304, and the adhesive tape is placed on the lower side and placed in a constant temperature bath at 80 ° C.
A suspending load of 1 kg is applied, and the shift or drop time of the tape after 1 hour is measured, and this is taken as the holding force.

4. Adhesive strength to polyurethane resin foam A laminate in which a polyester film side of an adhesive tape and a stainless steel plate made of SUS304 are attached with a double-sided adhesive tape, and a density of 0.05 g / cm cut into a width of 20 mm, a length of 100 mm and a thickness of 5 mm ³ of a polyurethane resin foam sheet was allowed to stand over 2 hours under an atmosphere of 5 ° C.,
The polyurethane foam was laminated using a 2 kgf roller so that the thickness would be 50%, left at 5 ° C. for 24 hours, and then the peel strength was measured in the 90 ° direction at a pulling speed of 300 mm / min.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

As can be seen from this table, in Examples 1 to 4 in which the temperature at which the logarithmic attenuation rate is maximized is -10 ° C or less, the tack of 0 ° C, the tack of 23 ° C, the holding power, and the adhesive force to the polyurethane resin foam. All of the above are good, but Comparative Examples 1 to 3 in which the temperature at which the logarithmic attenuation rate becomes maximum is -10 ° C or higher are good in tack at 23 ° C, but poor in tack at 0 ° C, holding power, and adhesive force to polyurethane resin foam. Therefore, the adhesive property at low temperature and the adhesiveness to the polyurethane resin foam are poor.

[0029]

As is apparent from the above description, the acrylic pressure-sensitive adhesive composition of the present invention contains an alkyl (meth) acrylate as a main component and has a pendulum type viscoelasticity at each temperature of -50 to + 100 ° C. Since the maximum value in the above temperature range when the logarithmic decrement measured by a measuring device is plotted against temperature is -10 ° C or less, it is excellent in tack at low temperature and is a polyurethane resin foam or polyethylene resin. It has excellent adhesiveness to synthetic resin foam such as foam and cohesive force. Therefore, the acrylic pressure-sensitive adhesive composition of the present invention can be suitably used for various purposes as various pressure-sensitive adhesive tapes and double-sided pressure-sensitive adhesive tapes.

[Brief description of drawings]

FIG. 1A is an explanatory diagram of a pendulum, and FIG. 1B is an explanatory diagram of a load, which are used when measuring a logarithmic decrement.

[Description of sign]

 A Pendulum 1 Cylinder 2 Frame material 21 Lower side of frame 3 Legs 4 Magnet attraction plate 5 Stopper 6 Load

Claims (1)

[Claims] 1. The above-mentioned when the logarithmic decrement measured with a pendulum type viscoelasticity measuring device is plotted against temperature at each temperature of -50 to + 100 ° C., which contains alkyl (meth) acrylate as a main component. A maximum value in a temperature range is -10 degreeC or less, The acrylic adhesive composition characterized by the above-mentioned.