JPS59538B2 - Adhesive for synthetic resin moldings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to adhesives for synthetic resin moldings, and in particular,
This invention relates to an adhesive suitable for attaching a synthetic resin molding to a sheet metal part of an automobile body.

In this specification, "parts" means "parts by weight."

After being attached to the car body, the molding is exposed to freezing outdoor conditions such as extreme heat and cold, and gasoline is often splashed onto the molding during refueling. In addition, automotive moldings are directly affected by the outside temperature, and due to temperature differences between daytime and nighttime, summer and winter, etc., expansion and expansion occurs between the molding and the sheet metal part.
Causes differential shrinkage.

For this reason, adhesives for automotive moldings are required to have weather resistance, oil resistance, heat resistance, cold resistance, etc., as well as adhesive strength that can overcome the difference in expansion and contraction between the molding and the sheet metal part. .

Conventionally, automotive moldings have been attached to the vehicle body by using double-sided adhesive tape, a combination of double-sided adhesive tape and silicone adhesive, or a combination of general rubber adhesive.

However, when double-sided adhesive tape is used, although it satisfies the requirements for oil resistance and heat resistance to some extent, it lacks adhesive strength that can overcome the difference in expansion and contraction between the molding and the sheet metal part, which poses a problem.

When double-sided adhesive tape and silicone adhesive are used together, there is a problem in that the curing time is extremely long. Further, in the case of a rubber adhesive, although the difference in expansion and contraction between the molding and the sheet metal part can be overcome to some extent, there are problems such as heat resistance and oil resistance. In particular, these problems are noticeable when an automobile molding is attached to a corner portion of a vehicle body due to the rebound elasticity of the molding. In view of the above, this invention provides that, when used as an adhesive when attaching a synthetic resin molding to a sheet metal part, the adhesive strength does not decrease even in high-temperature atmospheres such as intense heat, or even when exposed to gasoline, etc. Moreover, the synthetic resin molding has adhesive strength that can overcome the difference in expansion and contraction between the molding and the sheet metal part due to temperature changes in the outside air, and can maintain a good adhesive state between the molding and the sheet metal part for a long period of time. The purpose is to provide adhesives for

Another object of the present invention is to provide an adhesive for a synthetic resin molding which has good solution stability on both sides during sealing and after opening.

The gist of this invention is to graft polymerize an acrylic monomer to a urethane polymer synthesized by reacting a polyester polyol with a diisocyanate.
Synthesized by reacting an acrylic urethane polymer with an H group with polypropylene glycol and toluene diisocyanate A urethane prepolymer with NCO groups on both ends is synthesized by adding 11111i1 alcohol to a urethane polymer with NCO groups on both ends. A synthetic resin molding adhesive is made by reacting the urethane polymer to alkylate both ends of the urethane polymer and is dissolved in an organic solvent.

The adhesive of the present invention will be described in more detail below. Synthesis of acrylic urethane polymer This acrylic urethane polymer is prepared by mixing 1,100 parts of a urethane polymer having 0H groups at both ends and 21 to 50 parts of an acrylic monomer with an appropriate amount of an organic solvent. It is synthesized by adding and grafting an oxide catalyst.

Here, if the mixing ratio of acrylic monomer 2 is less than 1 part, the adhesive becomes too soft, and if it is more than 50 parts, the adhesive becomes too hard, both of which contribute to a decrease in adhesive strength.

Examples of the above-mentioned peroxide catalyst include penzoylpa J-oxide (hereinafter abbreviated as "BPO"), lauroyl peroxide, and tert-butyl peroxide.

Examples of the organic solvents include aromatic hydrocarbons such as benzene, toluene, and xylene, and methyl ethyl ketone (
Examples include ketones such as methyl isobutyl ketone (hereinafter abbreviated as "MEX") and methyl isobutyl ketone.

In addition, the organic solvent should be aromatic hydrocarbons/ketones = 60/4 rather than using aromatic hydrocarbons or ketones alone.
From the viewpoint of solution stability of the adhesive, it is preferable to mix and use them in a ratio of 0 to 40/60 (weight ratio). (1) Urethane polymer This urethane polymer is made by adding 4,4'-diphenylmethane diisocyanate (hereinafter referred to as "MDT") to polyalkylene adipate (hereinafter referred to as "PAA") in 0H/NC.
It has 0H groups at both ends and is obtained by reacting at a molar ratio of O=1/l to 1/0.85.

At this time, if the molar ratio of NCO exceeds 1, a urethane polymer having 0H groups at both ends cannot be obtained, and if the molar ratio of NCO is less than 0.85, sufficient adhesive strength cannot be obtained. In the above, PAA is ethylene glycol, 1,
It is obtained by reacting one type or a mixture of two types of 4-butanediol with adipic acid and has 0H groups at both ends, and examples thereof include polyethylene adipate, polybutylene adipate (hereinafter abbreviated as "PBA"), etc. .

PAA has a molecular weight of 500 to 60,001, preferably 150
0 to 3000 is used. At this time, the molecular weight is 500
If the molecular weight is less than 6,000, the adhesive becomes hard and brittle, and if the molecular weight exceeds 6,000, the adhesive becomes too soft, both of which contribute to a decrease in adhesive strength. (2) Acrylic monomer One type or a mixture of two or more types selected from the group consisting of methacrylic acid, lower alcohol esters of acrylic acid, 2-hydroxyethyl methacrylate, and acrylamide is used.

Adhesives using the latter group.

A crosslinking reaction occurs between linear molecules, and heat resistance is improved compared to adhesives using the former group that do not undergo a crosslinking reaction.

The lower alcohol esters include methyl methacrylate (hereinafter abbreviated as "MMA"), ethyl methacrylate (hereinafter abbreviated as "EMA"), n-propyl methacrylate, n-butyl methacrylate, benzyl methacrylate, methyl acrylate, ethyl acrylate, n-propyl Examples include acrylate, benzyl acrylate/etc.

→ Synthesis of urethane prepolymer This urethane prepolymer is produced by reacting polypropylene glycol (hereinafter abbreviated as "PPG") and toluene diisocyanate (hereinafter abbreviated as "TDI") at a molar ratio of 0H/NCO = 1/2. It has NCO groups at both ends to be synthesized.

When the molar ratio of NCO exceeds 2, unreacted diisocyanate remains and is extruded during use, resulting in harm to the human body.On the other hand, when it is less than 2, a urethane prepolymer with NCO groups at both ends is obtained. It does not react completely with the acrylic urethane polymer A described above.

PPG used has a molecular weight of about 5,000 to 40,001, which is undesirable, and 1,000 to 2,000.

At this time, if the molecular weight is less than 500, the adhesive becomes too hard, and if it is more than 4,000, it becomes too soft, resulting in a decrease in adhesive strength. (C) Synthesis of urethane polymer This urethane polymer is made by combining the above acrylic urethane polymer A and the above urethane prepolymer B at 0H/NCO=1
It has NCO groups at both ends and is synthesized by reacting at a molar ratio of /2.

At this time, if the molar ratio of NCO groups exceeds 2, urethane prepolymer B having NCO groups at both unreacted ends remains in the obtained urethane polymer, and during the alkylation described later, urethane prepolymer B becomes monohydric alcohol. When the molecular weight is less than 2, the molecular weight of the urethane polymer becomes too large and the solution stability of the adhesive decreases.

(Self) Alkylation of urethane polymer Monohydric alcohol is added to the urethane polymer C synthesized above at a molar ratio of 1 mole or more per mole of NCO1, and the N
The CO group and the OH group of the monohydric alcohol are reacted to alkylate both ends of the urethane polymer C.

At this time, any monohydric alcohol having 2 to 20 carbon atoms, such as ethanol, butanol, hexyl alcohol, stearyl alcohol, etc., can be used.

When synthesizing the urethane prepolymer B and urethane polymer C, an amine-based or tin-based urethanization catalyst may be used if necessary.

As amines, tertiary amines such as triethylenediamine, N-methylmorpholine, methylhexylamine, and dimethylpenzylamine are used as tin-based amines such as dibutyltin diacetate and dibutyltin dilaurate (hereinafter referred to as [DBTDL]).
).

Examples include organic tin compounds such as dimethyloctyltin and di-2-ethylhexyltin-bis(monobutyl maleate). Further, carbon black, dye, pigment, etc. may be added to this adhesive for coloring, if necessary.

The adhesive prepared as described above is applied to the back side of a synthetic resin molding, etc. by a method such as dip coating, spray coating, brush coating, knife coating, or roll coating.
If the molding is pressed onto the sheet metal part of the car body and left at room temperature for several hours or heated at a temperature of 60 to 100°C for several minutes, a strong adhesive layer will be formed between the molding and the sheet metal part. .

At this time, heating at a temperature of 100°C or higher is undesirable because there is a risk of deformation or thermal deterioration of the molding and sheet metal parts. When used for installation on
The adhesive strength does not decrease even in high-temperature environments such as extremely hot weather, or even when exposed to gasoline, etc., and has adhesive strength that can overcome the difference in expansion and contraction between the molding and the sheet metal part due to temperature differences in the outside air. However, good adhesion between the molding and the sheet metal part can be maintained.Also, since this adhesive is a urethane-based adhesive with alkylated ends, the adhesive solution will not evaporate both during sealing and after opening. Good stability.

Examples of the present invention will be shown below, and the adhesive properties thereof will be tested together with comparative examples to confirm the effects of the present invention. The adhesives of each example were synthesized by reacting each compound and each part shown in Table 1 as follows.

(1) Acrylic urethane polymer is obtained by reacting a mixture having the composition shown in column A in the table at 80°C for 3 hours in dry nitrogen gas, and then mixing each part of the acrylic monomer shown in the table to start polymerization. As an agent, BPOO. Add 5 parts,
The mixture was synthesized by stirring at 80° C. for 5 hours in dry nitrogen gas. (2
) The urethane prepolymer was prepared by adding DBTDLO. The mixture was synthesized by adding a portion of OOl and reacting at 80° C. for 3 hours in dry nitrogen gas.

(3) Acrylic urethane polymer 106 obtained in (1) above
6 parts and 32.4 parts of the urethane polymer obtained in (2) were reacted at 80°C for 3 hours in dry nitrogen gas, and the l-hydric alcohol shown in the table was added thereto, and 8' CX3O was added in dry nitrogen gas.
Adhesives of each example were synthesized by mln reaction.

Moreover, the adhesive of the comparative example is as follows.

Comparative example 1 200 parts of PBA (molecular weight approximately 2000) and MD
25 parts of I, 480 parts of toluene, and 32 parts of MEK were subjected to an 80'CX3h reaction in dry nitrogen gas, and to the urethane polymer, 2.8 parts of MMA1, 19.2 parts of glycidyl methacrylate, and BPCO. 5 parts were added thereto, and stirring was continued at 80° C. for 5 hours in dry nitrogen gas to synthesize an adhesive.

Comparative Example 2 Double-sided adhesive tape 561 (trade name: manufactured by Nitto Electric Industry Co., Ltd.) Comparative Example 3 Tosseal RTV-382 (manufactured by Toshiba Silicone Co., Ltd.) The molding used in each test example was manufactured as follows.

(a) Urethane mold Thermoplastic urethane "Pantex T-5168 (trade name; manufactured by Dainippon Ink and Chemicals Co., Ltd.) at 185 to 200
It was manufactured by extrusion from an extruder at ℃.

(b) Polyvinyl chloride mold The following formulation was extruded from an extruder at 150-170°C.

Polyvinyl chloride 100 parts Dioctyl phthalate 90 Barium dilaurate
1.5 Zinc Laurate
2 Dibutyltin dimaleate 1 The adherend is a sheet metal coated with a chlorinated rubber-urethane primer and urethane paint R-258H (product name: Nippon P Chemical).
After coating, the coating was dried at 75° C. for 1 hour.

For the test pieces in each test example, after applying or pasting the adhesive of each experimental example or comparative example on each molding shown in Table 2,
Immediately attach the molding to the adherend and apply shiatsu pressure for 15 minutes.
The test was performed for 2 seconds and left at room temperature for 3 days.

Adhesion was determined by measuring shear strength and splitting strength under the following conditions using the test piece prepared as described above, and the results are listed in Table 2.

The shear strength and splitting strength were measured using a tensile tester [TEN
STLON/UTM/5000-W (product name; manufactured by Toyo Sokki Co., Ltd.) was used at a tensile speed of 50 mm/Min.
I did it. In the shear test, the adhesion area was 2d (2 cm long x 1 wide)
CITL), 10d (vertical 10cm x width 1
cm). In the shear test, the molding and the adherend are pulled parallel to each other in opposite directions and the shearing force is measured. In the splitting test, the adherend is fixed horizontally and the edge of the molding is pulled in the vertical direction. It measures the force at which the adhesive surface splits when pulled up.

Water resistance test: After being immersed in a constant temperature water bath at 40°C for 726 hours, it was left at room temperature for 3 days.

Gasoline resistance test: After 1 hour immersion in commercially available gasoline, 1 hour at room temperature
I left it for days.

Heat resistance test: 300 hours at room temperature after being left in a constant temperature bath at 80℃
I left it alone.

From the results in Table 2, it can be seen that the adhesive of the present invention exhibits much stronger adhesive strength than the adhesive of the comparative example in all tests.

Claims (1)

[Scope of Claims] 1 A monohydric alcohol is added to a urethane polymer having NCO groups at both ends, which is synthesized by reacting the following acrylic urethane polymer A and the following urethane prepolymer B, and the both ends of the urethane polymer are converted into alkyl Adhesive for moldings made of synthetic resin that is dissolved in an organic solvent. (A) Polyalkylene adipate with OH groups at both ends (
However, the number of carbon atoms in alkylene is 2 and 4), and 4,4-diphenylmethane diisocyanate is added to OH/NCO=1/0.
．． A group of lower alcohol esters of acrylic acid or methacrylic acid, or a group of 2-hydroxyethyl methacrylate or acrylamide is added to 100 parts of a urethane polymer having OH at both ends synthesized by reacting at a molar ratio of 85 to 1. An acrylic urethane polymer synthesized by grafting 1 to 50 parts of one or more acrylic monomers selected from the group. (B) A urethane prepolymer having NCO groups at both ends, which is synthesized by reacting polypropylene glycol and toluene diisocyanate.