JP2019172881A - Moisture-curable reactive hot-melt adhesive composition - Google Patents

Abstract

To provide a moisture-curable reactive hot-melt adhesive composition that has excellent initial adhesiveness, and forms an adhesion layer of a low elastic modulus after moisture curing.SOLUTION: A moisture-curable reactive hot-melt adhesive composition has (A) a urethane prepolymer having an isocyanate group and (B) an acrylic polymer, the (B) acrylic polymer having a glass transition temperature of 50°C or more and a weight average molecular weight of 50,000 or more, and the acrylic polymer content being 5-25 mass% based on the total amount of the composition.SELECTED DRAWING: None

Description

  The present invention relates to a moisture curable reactive hot melt adhesive composition.

  A hot-melt adhesive is a solvent-free adhesive with a low load on the environment or the human body, and can be bonded for a short time, so that it is suitable for improving productivity. Hot melt adhesives can be broadly classified into two types, those based on thermoplastic resins and those based on reactive resins. Of these, hot melt adhesives based on reactive resins cause a curing reaction after bonding, so the adhesive strength and heat resistance after bonding are higher than those based on thermoplastic resins. It is widely used for applications that require adhesive reliability.

  When using a reactive resin, a urethane prepolymer having an isocyanate group at the terminal is mainly used. A reactive hot-melt adhesive mainly composed of a urethane prepolymer exhibits a certain degree of adhesive strength in a short time due to cooling and solidification of the adhesive itself after bonding. Thereafter, the isocyanate group at the terminal of the urethane prepolymer reacts with moisture in the air or on the surface of the adherend, whereby high molecular weight and crosslinking occur. And since the cohesive force of an adhesive agent increases and heat resistance is expressed, good adhesive strength is exhibited even during heating. As such an adhesive, a reactive hot-melt adhesive composition comprising a polyurethane prepolymer, a thermoplastic resin, and a tackifier with improved initial adhesive strength is known (see, for example, Patent Document 1). .)

Japanese Patent Laid-Open No. 2015-052063

  By the way, the hot-melt adhesive may be required to have initial adhesiveness immediately after bonding, depending on the use of the article.

  When initial adhesiveness is imparted to a hot melt adhesive, a highly crystalline polyol may be used as a raw material in order to increase the initial cohesive strength of the adhesive. However, the use of these materials tends to increase the tensile modulus of the adhesive layer after moisture curing, which is not suitable for applications requiring flexibility. On the other hand, when an amorphous polyol having a low glass transition temperature is used as a raw material in order to soften the adhesive layer, the initial adhesiveness tends to decrease.

  Accordingly, an object of the present invention is to provide a moisture curable reactive hot melt adhesive composition that has good initial adhesiveness and forms a low elastic modulus adhesive layer after moisture curing.

  The present invention provides a moisture-curable reactive hot melt adhesive composition as shown in the following [1] to [3].

[1] (A) A urethane prepolymer having an isocyanate group and (B) an acrylic polymer, the glass transition temperature of the (B) acrylic polymer being 50 ° C. or higher, and the weight average molecular weight being 50,000 or higher, A moisture-curable reactive hot melt adhesive composition, wherein the polymer content is 5 to 25% by mass based on the total amount of the composition.
[2] In creep recovery measurement at 20 ° C. using a rotary rheometer, the maximum strain value when stress of 10000 Pa is applied is 70% or less, and the strain recovery rate after releasing the stress is 40% or more, The moisture curable reactive hot melt adhesive composition according to [1].
[3] Moisture curing according to [1] or [2] above, wherein the peel adhesion strength at 23 ° C. after 5 minutes of bonding is 3 N / 25 mm or more and the melt viscosity at 120 ° C. is 30 Pa · s or less. Type reactive hot melt adhesive composition.

  According to the present invention, it is possible to provide a moisture-curable reactive hot melt adhesive composition that has good initial adhesiveness and forms an adhesive layer having a low elastic modulus after moisture curing.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  In this specification, “moisture-curable reactive hot melt adhesive composition” means a high molecular weight by reacting with moisture (humidity) in the air or on the surface of the adherend, and exhibiting functions such as adhesiveness. Means what to do.

  The moisture-curable reactive hot melt adhesive composition according to an embodiment (hereinafter sometimes simply referred to as “adhesive composition”) includes (A) a urethane prepolymer having an isocyanate group, and (B) an acrylic. A polymer is contained, the glass transition temperature of the (B) acrylic polymer is 50 ° C. or higher, the weight average molecular weight is 50,000 or higher, and the acrylic polymer content is 5 to 25% by mass based on the total amount of the composition. .

[(A) component: urethane prepolymer having an isocyanate group]
The urethane prepolymer having an isocyanate group is usually obtained by reacting a polyol compound (a compound having two or more hydroxyl groups in the molecule) with a polyisocyanate compound (a compound having two or more isocyanate groups in the molecule). it can.

  Examples of the polyol compound include polyester polyol, polyether polyol, acrylic polyol, polyolefin polyol, polybutadiene polyol, polyisoprene polyol, rosin-modified polyol, polyethylene butylene polyol, polycarbonate polyol, and polycaprolactone polyol.

  Examples of the polyisocyanate compound include diphenylmethane diisocyanate, dimethyldiphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, p-phenylene diisocyanate, and isophorone diisocyanate.

  The mixing ratio of the polyisocyanate compound and the polyol compound when synthesizing the urethane prepolymer having an isocyanate group is an isocyanate group (NCO) equivalent of the polyisocyanate compound / a hydroxyl group (OH) equivalent of the polyol compound, preferably 1.5. As mentioned above, More preferably, it is the range of 1.5-3.0. When the mixing ratio of the polyisocyanate compound and the polyol compound is 1.5 or more, the viscosity of the resulting urethane prepolymer falls within an appropriate range, so that workability can be improved. When the mixing ratio of the polyisocyanate compound and the polyol compound is 3.0 or less, foaming can be suppressed during the moisture curing reaction, and the adhesiveness can be improved.

[(B) component: acrylic polymer]
The acrylic polymer is usually used as a resin modifier. By including an acrylic polymer in the adhesive composition, high initial adhesiveness can be imparted.

  The content of the acrylic polymer is 5 to 25% by mass based on the total amount of the composition. When the content of the acrylic polymer is 5% by mass or more based on the total amount of the composition, desired initial adhesiveness is easily obtained. Moreover, the raise of the melt viscosity of an adhesive agent can be suppressed as content of an acrylic polymer is 25 mass% or less on the basis of the composition whole quantity. The content of the acrylic polymer is preferably 23% by mass or less, more preferably 20% by mass or less.

  Examples of commercially available acrylic polymers include DYNACOLL AC (Evonik Degussa Co., Ltd., a copolymer of methyl methacrylate and n-butyl methacrylate, “DYNACOLL” is a registered trademark), and the like. Specifically, DYNACOLL AC1631 (Tg (glass transition temperature); 57 ° C., Mw (weight average molecular weight); 60,000), DYNACOLL AC1630 (Tg; 60 ° C., Mw; 550,000), DYNACOLL AC1632 (Tg; 55 ° C, Mw; 650,000), DYNACOLL AC1750 (Tg; 65 ° C, Mw; 140,000), DYNACOLL AC4830 (Tg; 82 ° C, Mw; 60,000), DYNACOLL AC2740 (Tg; 70 ° C, Mw; 8) ) Etc.

  In the adhesive composition according to this embodiment, polyurethane, an ethylene copolymer, a propylene copolymer, a vinyl chloride copolymer, an acrylic copolymer, a styrene-conjugated diene block copolymer, if necessary. Thermoplastic polymers such as coalescence, rosin resin, rosin ester resin, hydrogenated rosin ester resin, terpene resin, terpene phenol resin, hydrogenated terpene resin, petroleum resin, hydrogenated petroleum resin, coumarone resin, ketone resin, styrene resin, modified Tackifying resins such as styrene resin, xylene resin, epoxy resin, catalysts such as dibutyltin dilaurate, dibutyltin dioctate, dimethylcyclohexylamine, dimethylbenzylamine, trioctylamine, pigments, antioxidants, UV absorbers, surfactants In addition, flame retardants, fillers and the like may be added.

  The adhesive composition according to this embodiment has a maximum strain value of 70% or less when a stress of 20 ° C. and 10000 Pa is applied in a creep recovery measurement with a rotary rheometer, and a strain recovery rate after releasing the stress is 40%. % Or more is preferable. By satisfying these numerical ranges, the initial adhesiveness of the adhesive composition can be higher.

  The rotary rheometer for measuring creep recovery can measure the strain change when a sample melted and set at 120 ° C is cooled to 20 ° C at a constant speed, and then any stress is applied to the sample and released. If it is an apparatus, it will not restrict | limit in particular.

  The melt viscosity at 120 ° C. of the adhesive composition according to this embodiment is preferably 30 Pa · s or less, more preferably 20 Pa · s or less, and even more preferably 10 Pa · s or less. When the melt viscosity at 120 ° C. is 10 Pa · s or less, various coating apparatuses can be used, and there is a tendency that a stable discharge property can be obtained particularly when coating is performed at a low coating amount.

  The initial adhesive strength according to this embodiment is preferably 3 N / 25 mm or more, more preferably 5 N / 25 mm or more, and even more preferably 10 N / 25 mm or more after 5 minutes of bonding at room temperature (23 ° C.). When the adhesive strength is 3 N / 25 mm or more, it tends to be applicable as an adhesive for various uses.

  The adhesive composition according to this embodiment is produced by a method including a step of obtaining a urethane prepolymer having an isocyanate group by reacting a polyol compound and a polyisocyanate compound.

  In the adhesive composition according to this embodiment, for example, a urethane compound having an isocyanate group can be obtained by reacting a polyol compound and a polyisocyanate compound in the presence of an acrylic polymer.

  The moisture curable reactive hot melt adhesive can be formed by applying the adhesive composition according to this embodiment. The coating method is not particularly limited, and examples thereof include a method using a coating device such as a die coater, a roll coater, and a spray. A dispenser is suitable for application to narrow parts such as small parts.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

  The raw materials used are as follows.

Polyol compound (a): Polyester polyol (ethylene glycol, neopentyl glycol, ester of adipic acid and isophthalic acid, number average molecular weight: 2000)
Polyol compound (b): Polypropylene glycol (manufactured by Asahi Glass Co., Ltd., trade name “Exenol 2020” (“Excenol” is a registered trademark))
Polyol compound (c): propylene oxide adduct of bisphenol A (trade name “BPX-11” manufactured by ADEKA Corporation)
Polyisocyanate compound: Diphenylmethane diisocyanate (trade name “Millionate MT” manufactured by Tosoh Corporation)
Acrylic polymer (a): acrylic polymer (Evonik Degussa, trade name “DYNACOLL AC1750”, weight average molecular weight: 140,000, glass transition temperature: 65 ° C.)
Acrylic polymer (b): Acrylic polymer (Evonik Degussa, trade name “DYNACOLL AC1630”, weight average molecular weight: 55,000, glass transition temperature: 60 ° C.)
Acrylic polymer (c): Acrylic polymer (Kuraray Co., Ltd., trade name “LA-2140”, weight average molecular weight: 80,000, glass transition temperature: −22 ° C.)

Example 1
7.3 parts by mass of the acrylic polymer (a) and 29.2 parts by mass of the polyol compound (b) are put into a 1 L glass round bottom flask, and the internal temperature is from room temperature (25 ° C.) to 95 ° C. under a nitrogen gas stream. The acrylic polymer was dissolved by mixing and stirring while raising the temperature. Furthermore, 42.3 parts by mass of the polyol compound (a) and 1.5 parts by mass of the polyol compound (c) were added and dehydrated for 1 hour under reduced pressure while stirring. Thereafter, the pressure was returned to normal pressure with nitrogen, 19.7 parts by mass of diphenylmethane diisocyanate was added, the internal temperature was raised to 110 ° C., and the reaction was carried out for 1 hour under a nitrogen stream. Thereafter, dehumidification under reduced pressure was further performed at 110 ° C. for 1 hour to obtain a moisture-curable reactive hot melt adhesive composition containing a urethane prepolymer having an isocyanate group.

(Example 2)
Acrylic polymer (a) 13.5 parts by mass, polyol compound (a) 39.5 parts by mass, polyol compound (b) 27.2 parts by mass, polyol compound (c) 1.4 parts by mass, diphenylmethane diisocyanate 18.4 parts by mass A moisture-curable reactive hot melt adhesive composition was obtained in the same manner as in Example 1 except that the composition was changed to the part.

(Example 3)
Acrylic polymer (a) 19.1 parts by mass, polyol compound (a) 36.9 parts by mass, polyol compound (b) 25.5 parts by mass, polyol compound (c) 1.3 parts by mass, diphenylmethane diisocyanate 17.2 parts by mass A moisture-curable reactive hot melt adhesive composition was obtained in the same manner as in Example 1 except that the composition was changed to the part.

(Example 4)
Example 1 with the exception that 13.8 parts by mass of the acrylic polymer (b), 41.4 parts by mass of the polyol compound (a), 27.6 parts by mass of the polyol compound (b), and 17.2 parts by mass of diphenylmethane diisocyanate were used. Similarly, a moisture curable reactive hot melt adhesive composition was obtained.

(Comparative Example 1)
Example 1 except that the acrylic polymer (a) was changed to 28.6 parts by mass, the polyol compound (a) 34.3 parts by mass, the polyol compound (b) 22.9 parts by mass, and diphenylmethane diisocyanate 14.3 parts by mass. Similarly, a moisture curable reactive hot melt adhesive composition was obtained.

(Comparative Example 2)
Example 1 except that acrylic polymer (c) 14.0 parts by mass, polyol compound (a) 42.1 parts by mass, polyol compound (b) 28.1 parts by mass, diphenylmethane diisocyanate 15.8 parts by mass Similarly, a moisture curable reactive hot melt adhesive composition was obtained.

(Comparative Example 3)
50.0 parts by mass of the polyol compound (a) and 33.3 parts by mass of the polyol compound (b) are charged into a 1 L glass round bottom flask and mixed while raising the internal temperature to 95 ° C. in a nitrogen gas stream. Stir and dehydrate for 1 hour under reduced pressure. Thereafter, the pressure was returned to normal pressure with nitrogen, 16.7 parts by mass of diphenylmethane diisocyanate was added, the internal temperature was raised to 110 ° C., and the reaction was carried out for 1 hour under a nitrogen stream. Thereafter, dehumidification under reduced pressure was further performed at 110 ° C. for 1 hour to obtain a moisture-curable reactive hot melt adhesive composition containing a urethane prepolymer having an isocyanate group.

[Measurement of creep recovery]
Creep recovery of the moisture curable reactive hot melt adhesive compositions of Examples 1 to 4 and Comparative Examples 1 to 3 was measured using a rotary rheometer (DHR-2 manufactured by TA Instruments) under the following conditions.
Geometry: Diameter 20mm cone GAP: 0.057mm
Temperature history: Cooled from 120 ° C. to 20 ° C. at 40 ° C./min and held at 20 ° C. Stress: 10000 Pa was applied for 2 seconds after reaching 20 ° C., then stress was released and left for 28 seconds Strain maximum : Maximum strain value when stress is applied Strain recovery rate: Maximum strain value and minimum strain value when stress is applied and after release is calculated.
Was calculated.
Strain recovery rate = (maximum strain value−minimum strain value) × 100 / maximum strain value

[Measurement of adhesive strength (peeling adhesive strength)]
The peel adhesion strengths of the moisture curable reactive hot melt adhesive compositions of Examples 1 to 4 and Comparative Examples 1 to 3 were measured using a tensile tester (manufactured by Shimadzu Corporation) under the following conditions.
The measurement was performed 5 minutes after bonding.
Base material: Polyurethane fabric Adhesive layer thickness: approx. 0.08mm
Adhesion width: 25mm
Tensile speed: 100 mm / min
Test temperature: 23 ° C

[Measurement of melt viscosity]
The melt viscosity of the moisture curable reactive hot melt adhesive compositions of Examples 1 to 4 and Comparative Examples 1 to 3 was adjusted to the following conditions using a BH-HH type small amount rotational viscometer (manufactured by Toki Sangyo Co., Ltd.). Measured. The results are shown in Table 1.
Rotor: No. 4 rotor Sample amount: 15 g
Number of revolutions: 10 revolutions / minute (rpm)
Temperature: 120 ° C

As shown in Table 1, each of the moisture curable reactive hot melt adhesive compositions of Examples 1 to 4 has a maximum strain value of 70% or less and a strain recovery rate of 40% or more in the creep recovery measurement. The initial peel adhesion strength was 3 N / 25 mm or more, and the melt viscosity was 30 Pa · s / 120 ° C. or less.
On the other hand, Comparative Example 1 in which the content of the acrylic polymer (a) exceeds 25% by mass is not practical because the melt viscosity is high and the applicability is poor. In Comparative Example 2 containing the acrylic polymer (c) having a low glass transition temperature and Comparative Example 3 not containing the acrylic polymer, the maximum strain value is 70% or more or the strain recovery rate is 40% or less in the creep recovery measurement. Yes, the initial peel adhesion strength was less than 3 N / 25 mm.

Claims (3)

  (A) A urethane prepolymer having an isocyanate group and (B) an acrylic polymer, the glass transition temperature of the (B) acrylic polymer is 50 ° C. or higher, the weight average molecular weight is 50,000 or higher, and the acrylic polymer is contained A moisture-curable reactive hot-melt adhesive composition, the amount of which is 5 to 25% by mass based on the total amount of the composition.   In creep recovery measurement at 20 ° C. using a rotary rheometer, the maximum strain value when stress of 10000 Pa is applied is 70% or less, and the strain recovery rate after releasing the stress is 40% or more. The moisture-curable reactive hot melt adhesive composition described.   The moisture-curable reactive hot according to claim 1 or 2, wherein a peel adhesion strength at 23 ° C after 5 minutes of bonding is 3 N / 25 mm or more and a melt viscosity at 120 ° C is 30 Pa · s or less. Melt adhesive composition.