JPH0422954B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel structural adhesive composition that can be bonded in seconds and has excellent heat resistance, cold resistance, and durability. Conventionally, α has been used as an adhesive that can be bonded in seconds.
- Although there are adhesives typified by cyanoacrylates, they have poor heat resistance, cold resistance, and impact resistance, and are extremely unreliable for use as structural adhesives. On the other hand, there are so-called hot melt adhesives made of thermoplastic elastomers that can be bonded in seconds, but they often have poor heat resistance and creep when stress is applied for a long time above the glass transition temperature. The reality is that there are no adhesives that are well-balanced and highly durable under a wide range of environments, and are widely used in applications where these drawbacks are acceptable, such as bonding cloth and wood. In an attempt to solve the above-mentioned drawbacks using hot melt adhesives, methods of blending thermosetting resins or making them self-crosslinking have been proposed.
In both cases, the heat curing conditions are harsh and require a long time, and bonding in seconds has not yet solved the above drawbacks. For example, nylon and epoxy adhesives are well known, but they require several tens of minutes of heat curing time, resulting in poor productivity and a major obstacle. In addition, according to the proposal by Mr. Nakao et al. in the 11th Adhesion Research Presentation Abstracts P9 (1973), epoxy resin should be applied thinly onto an amorphous saturated polyester elastomer film, or the surface of the adherend should be coated in advance. The company proposes a method such as applying it as a primer to the surface, but the T-peel strength under normal conditions is sufficiently high, it is possible to bond in seconds as described above, and it also has good thermal strength, durability, and creep resistance. Important performance requirements such as these have not been sufficiently resolved. The present invention is based on crystalline blocks identified as a result of intensive studies to meet the above-mentioned needs, that is, to obtain a new structural adhesive that can be bonded in seconds and has excellent heat resistance, cold resistance, durability, and creep resistance. The inventors have discovered that these objects can be achieved by using a thermoplastic elastomer in combination with a specified epoxy resin, and have thus arrived at the present invention. That is, the present invention provides (A) a number average molecular weight in the range of 1 to 500,000 and a general formula (However, R ₁ is a divalent group that remains after removing the hydroxyl group from an organic diol with a molecular weight of 303 or less,
R ₂ is the divalent group that remains after removing the carboxyl group from aromatic and aliphatic dicarboxylic acids with a molecular weight of 350 or less, and R ₃ is the terminal hydroxy group removed from polytetramethylene glycol with a number average molecular weight of 400 to 3000. B is a divalent group that remains after removal, and n is a number average degree of polymerization in the range of 1 to 20. )
A structural adhesive composition comprising 1 to 40 parts by weight of an epoxy resin having a number average molecular weight of 450 to 30,000 and having at least 1.2 or more glycidyl groups in the molecule. . In the composition of the present invention, it is preferable to contain 1 to 5 parts by weight of the silane coupling agent (C) per 100 parts by weight of the crystalline thermoplastic elastomer (A). In addition, component (A) is obtained by using dimethyl terephthalic acid or terephthalic acid as the dibasic acid component and one or more of ethylene glycol, 1,4 butanediol, and 1,6-hexanediol as the glycol component. A polyetherester elastomer having a number average molecular weight of 30,000 to 200,000 obtained by reacting a polyalkylene phthalate having a terminal methyl carboxyl group or a carboxyl group with a polytetramethylene glycol having a number average molecular weight of 500 to 2,000 is preferably used. In the present invention, the crystalline polyester chain length component (hereinafter referred to as polyalkylene phthalate) constituting component (A) is as shown below so that the polyether ester elastomer, which is the final component (A), exhibits crystallinity. It is assumed that raw materials are appropriately selected and used, but the terminal groups of polyalkylene phthalate are carboxyl groups (including anhydride and alcohol ester groups, hereinafter collectively referred to as carboxyl groups) terminals or hydroxyl groups depending on the final elastomer. Either one of the terminal groups is selected as appropriate. That is, as a method for obtaining polyalkylene phthalate, for example, terephthalic acid, dimethyl terephthalate, isophthalic acid, tetrachlorophthalic anhydride,
Phthalic acids such as tetrachloroterephthalic acid, phthalic anhydride, orthophthalic acid, alcohol esters of phthalic acid, phthalic anhydride (hereinafter referred to as aromatic dibasic acid component), adipic acid, azelaic acid, succinic acid , succinic anhydride, sebacic acid, and aliphatic dibasic acids such as ethylene glycol, propylene glycol, 1,4 butanediol, neopentyl glycol, 1,5-pentanediol, 1,6 hexanediol, 3,9
-bis(1,1 dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxa[5,5]
Organic diols such as undecane (hereinafter abbreviated as spiroglycol) and the like can be easily obtained by conventionally known methods, ie, dehydration condensation or transesterification reaction (hereinafter referred to as esterification). In addition, when obtaining the polyalkylene phthalate, it is necessary to use the aliphatic dibasic acid component within a range that does not inhibit the crystallinity of the polyalkylene phthalate.
Also, for the purpose of obtaining heat resistance, durability, and creep resistance of the present invention, it is preferable that the proportion of para- or meta-substituted aromatic dibasic acids to the total dibasic acids be 80% or more, preferably 90% or more. It is particularly preferable that Alternatively, polyalkylene phthalate may be obtained by ring-opening addition of terephthalic acid or isophthalic acid and ethylene oxide or tetrahydrofuran, followed by esterification reaction with a dibasic acid. In the present invention, the number average degree of polymerization n of the polyalkylene phthalate is set in the range of 1 to 20 because n is 20.
This is because the above is unsuitable because the cold resistance and impact resistance deteriorate. In the present invention, when the polyalkylene phthalate is terminated with a carboxyl group, this is achieved by reacting the dibasic acid component in excess of the number of moles of the dibasic acid component relative to the number of moles of the organic diol component. In addition, when the polyalkylene phthalate is to have a hydroxyl group at its terminal end, the reaction can be achieved in the opposite manner, that is, by reacting with an excess number of molar equivalents of the organic diol relative to the number of molar equivalents of the dibasic acid component. In the present invention, the polyether ester elastomer which is component (A) can be obtained by reacting the polyalkylene phthalate described above with polytetramethylene glycol having a number average molecular weight of 400 to 3,000, preferably 500 to 1,500. The polytetramethylene glycol is a polyether diol obtained by ring-opening polymerization of tetrahydrofuran, which constitutes the amorphous portion of the block elastomer, and is particularly useful for improving the cold resistance and impact resistance of adhesives. It is thought that this contributes. The ratio of polyalkylene phthalate and polytetramethylene glycol to be used is based on the number average of the block type polyether ester elastomer finally obtained, with the weight of polytetramethylene glycol in the final elastomer being in the range of 5 to 70%. It may be adjusted so that the molecular weight is from 10,000 to 500,000, preferably from 30,000 to 200,000, and is generally obtained by a known method, that is, by esterification or organic diol removal reaction. Specifically, you should know the number average molecular weight of each raw material, polyalkylene phthalate and polytetramethylene glycol, calculate the theoretical equivalent ratio, and work around it, especially when using polyalkylene phthalate with a terminal hydroxyl group. For this, methods such as obtaining (A) by removal of organic diol reaction are applied. Crystallinity in the present invention refers to a state in which the polymer chains forming the polymer have a certain amount of coordination assembly state (often partial), and generally at room temperature. It is opaque or translucent by itself, and the presence or absence of crystallinity can be easily determined by methods such as X-ray diffraction. Known catalysts, promoters, and stabilizers may be used in the reactions such as esterification or deorganic diol removal, which are the means for synthesizing the elastomer of the present invention, and the reaction system can be dissolved without a solvent or in an inert state. If an organic solvent is used, it can be obtained by removing the solvent under reduced pressure, or by precipitating it in a solvent that does not dissolve the component (A) to be produced, and then drying it. I can do it. The epoxy resin which is component (B) in the present invention is an epoxy resin having a number average molecular weight of 450 to 30,000 and having at least 1.2 or more glycidyl groups on average in the molecule, such as bisphenol A or Relatively high-molecular bisphenol type epoxy resin derived from bisphenol F and epichlorohydrin, novolac type epoxy resin derived from novolac phenol and epichlorohydrin, addition of ethylene oxide or propylene oxide to bisphenol A or bisphenol F Typical examples are epoxy resins that are compatible with the polyetherester elastomer (A), such as aliphatic epoxy resins obtained by reacting epichlorohydrin with epichlorohydrin, and epoxy resins further modified using these epoxy resins. For example, epoxy resins that have been grafted in a branched manner through ring-opening addition of polyoxycarboxylic acids, butyllactone, caprolactone, etc., and nitrile-butadiene rubbers that have terminal carboxyl groups or amino groups that have been pre-reacted. It may also be a rubber-modified epoxy resin with a rubber-modified epoxy resin, or a so-called HI-modified epoxy resin in which a rubber component is stably dispersed and grafted to a certain size. Here, the number average molecular weight of the epoxy resin is 450 or more,
The range of 30,000 or less is because if it is 450 or less, the adhesive composition tends to become extremely soft and has poor heat resistance.
If it exceeds 30,000, the compatibility with the component (A) elastomer will be extremely poor, and the effect will be significantly impaired. The effect of component (B) of the present invention, epoxy resin, is
By using 1 to 40 parts by weight, preferably 3 to 20 parts by weight, per 100 parts by weight of component (A), extremely excellent adhesive performance is exhibited for reasons unknown. The epoxy resin, component (B), is probably effective as a crosslinking agent for the crystalline block thermoplastic elastomer polyetherester elastomer, component (A), and greatly improves the wetting properties and affinity for various adherends. We believe that the combination of improved adhesive properties and the generation of graft points results in excellent adhesive properties. In the present invention, the silane coupling agent (c) refers to γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β
(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, N-β-(N- Typical examples include vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride, and (A)
It is preferable to use 1 to 5 parts by weight per 100 parts by weight of the crystalline block type thermoplastic elastomer. Even if 5 parts by weight or more is added, no decrease in adhesive strength is observed, but the adhesive may foam, which is not preferable. (C) By using a silane coupling agent, there is a significant improvement in the reliability of adhesive strength mainly to metals, that is, long-term weather resistance, water resistance, moisture resistance, impact resistance, etc. In the present invention, in addition to (A) a crystalline block type thermoplastic elastomer, (B) an epoxy resin, and (C) a silane coupling agent, the previously known (D) latent epoxy curing agent, (E) an epoxy A curing accelerator may be used in combination, and it is particularly preferable to use it for the purpose of improving heat resistance. That is, as the latent epoxy curing agent (D), dihydrazide compounds such as dicyandiamide, adipic acid dihydrazide, isophthalic acid dihydrazide, dodecanoic acid dihydrazide, etc.
3,3'-diaminodiphenylsulfone, 4-4'-
It is also possible to use 1 to 25 parts by weight of one or more of diaminophenyl sulfonate, dodecanedicarboxylic acid, _BF3 /amine complex, imidazoles and their derivatives, urea resin, etc. per 100 parts by weight of the epoxy resin. , (E) as an epoxy curing accelerator, 3-
p-chlorophenyl-1,1-dimethylurea 3,
Use 1 to 5 parts by weight of tertiary amines such as 3-p-dichlorophenyl 1,1-dimethylurea, tris(NN'dimethylaminomethyl)phenol, dimethylbenzylamine, or complexes thereof per 100 parts by weight of the epoxy resin. You can also do it. The form of the structural adhesive in the present invention is not particularly limited, and may be in the form of a film, powder, pellet, or in some cases, a liquid that can be dissolved in an organic solvent that serves as a good solvent. Further, the structural adhesive of the present invention may be heated and mixed immediately before use using a hot melt applicator having a mixing function, and there are no particular restrictions on the method of use or application. Furthermore, known fillers, pigments, solvents, stabilizers, antioxidants, thixotropic agents, plasticizers, etc. may be mixed in advance into the structural adhesive of the present invention. Furthermore, there are no particular restrictions on the method of blending the structural adhesive of the present invention;
(A) Crystalline block type thermoplastic elastomer is dissolved in advance, (B) epoxy resin and (C) silane coupling agent, and optionally (D) latent epoxy curing agent, (E) epoxy curing accelerator. It may be obtained by adding and blending them all at once or sequentially, for example, using an extruder at the lowest possible temperature (100 to 200
Preferably, the compounding and extrusion is carried out at temperatures below Alternatively, after dissolving (A) the crystalline block type thermoplastic elastomer in a good solvent in advance, (B) an epoxy resin, (C) a silane coupling agent, etc. are added, and the solvent is removed under reduced pressure. It can also be obtained by extruding (A) a crystalline block type thermoplastic elastomer and (B) an epoxy resin into a poor solvent and drying. In addition, (A) the crystalline block type thermoplastic elastomer is made into a film, powder, or pellet form in advance by an appropriate method, and then the required amount of a mixture of (B) epoxy resin, (C) silane coupling agent, etc. is applied. Alternatively, the required amount of (B) epoxy resin, (C) silane coupling agent, etc. may be applied to the surface of the adherend, and then (A) crystalline block type thermoplastic elastomer may be applied. It is also possible to use a method that combines the formulation and bonding method, such as sandwiching and heat bonding. It is preferable that the adhesive layer be uniform, but there is no problem even if the adhesive layer is partially dispersed. Any processing method may be adopted as appropriate. Although the use of the structural adhesive of the present invention is not particularly limited, it is suitable for bonding metal materials. In other words, it is ideal for adhering metals such as iron, aluminum, tinplate, stainless steel, lead, and copper, as well as for bonding other metal materials such as FRP or plastic materials,
For example, adhesion of plastic molding materials such as polyester, acrylic, acrylonitrile-butadiene-styrene copolymer, epoxy resin, nylon resin, polycarbonate resin, phenol resin, urethane resin, melamine resin, polyethylene, polypropylene, and the above metal material and plastic rubber material. For example, it can be used for adhesion of plastic rubber molding materials such as vinyl chloride rubber, nitrile rubber, acrylic rubber, and urethane rubber, and for adhesion of plastic-coated steel plates, glass, ceramics, cloth, wood, etc. There are no particular restrictions on the conditions for using the structural adhesive of the present invention, but the thickness of the adhesive layer should be 20 to 300 μm, preferably 30 to 100 μm, and the surface temperature of the adherend should be 150 to 300°C. , preferably in the temperature range of 180 to 250°C for 1 to 60 seconds, and then allowed to cool or rapidly cool. There are no particular limitations on the heating device, etc., but the adhesive heating temperature increase rate is sufficient. Using a high-frequency heating bonding device that can be used quickly, it is possible to reach the target temperature from room temperature in 1 to 3 seconds, and in applications where productivity is important, it is possible to reach the target temperature in 1 to 30 seconds.
Adhesion is completed within seconds. Examples related to the present invention are shown below, but the present invention is not particularly limited or restricted, and parts and % shown below mean parts by weight and % by weight, respectively. Furthermore, although the bonding method used to illustrate the embodiments of the present invention will be described, the bonding method is not particularly limited. (a) Hot plate method: Prepare a Teflon-coated hot plate set to a constant temperature condition, place two adhered test pieces on it, heat it, and when the temperature reaches the specified temperature, apply the adhesive to the test piece. Place the specimen on one side, immediately overlap it with the other specimen, heat press it under a load of about 100 to 300 g/cm ² for a certain period of time, take it out, and quench it in water while keeping it pressed with a clamp. (b) High-frequency heating method; 200V, 5KW, high-frequency heating device with a transistor inverter type oscillator with an output frequency of 25KHz and a heating oscillation coil made of copper pipes wound in a coiled manner (with the test piece located in the center). (Shimada Rika Kogyo product, model HAD−
Prepare a molded Teflon jig as a clamping jig using 502H), sandwich adhesive between the test pieces in advance, and fix the test pieces with the special jig so that they do not shift. Place the tool so that it is located in the center of the coil. The output of each of the high-frequency adhesive heating apparatuses having a built-in three-stage output regulator is set to achieve the desired temperature condition, and the oscillation button is activated to generate heat in the adherend by passing a high-frequency current onto the heating coil. After heat-pressing at a constant temperature for a certain period of time, the pieces were allowed to cool or were rapidly cooled to prepare adhesion evaluation test pieces. The test was conducted using the above-mentioned high-frequency heating device only when the main adherend was iron, and the heat generation rate was able to reach from room temperature to 200℃ in 2 seconds, and then remained constant at the same temperature. It is a device that can be held. In addition, as a means of clamping when hot, a press cylinder that can be raised and lowered by compressed air is installed so that light pressing can be performed from the outside of the special clamping jig. It's getting old. In addition, the number of equivalents of hydroxyl groups in 1000 g of resin described in the examples is based on the hydroxyl value of the resin "acetylation method of acetic anhydride-pyridine" (Ber, 34 , 3354
This is the value calculated from the value obtained using the method in ~3358 (1901). Example 1 Synthesis of crystalline polyalkylene phthalate: Bishydroxyethyl terephthalate (addition reaction of terephthalic acid and ethylene oxide ) 828 parts and 664 parts of isophthalic acid
The final reaction temperature was 230°C.
The reaction was carried out while the water produced was distilled off. Obtained polyalkylene phthalate (A-1)
shows crystallinity, and from the measurement of acid value and hydroxyl value, 1.53 equivalent of carboxyl group and 0.04 equivalent in 1000 g of resin.
It was a polyalkylene phthalate (A-1) having an equivalent amount of hydroxyl groups and a number average molecular weight of 1274 with a number average degree of polymerization n≈2.5. Example 2 970 parts of dimethyl terephthalic acid, 180 parts of 1,4-butanediol, and 236 parts of 1,6-hexanediol were charged into a reactor similar to that used in Example 1, and heated and melted to produce 0.03% tetrabutoxytitanium. In addition, the final reaction temperature was raised to 230°C, and the reaction was carried out while distilling the methanol produced. Obtained polyalkylene phthalate (A-2)
shows crystallinity, and the infrared absorption spectrum shows that all terminals are methyl carboxyl groups, and as measured by GPC (polystyrene equivalent value),
The polyalkylene phthalate (A-2) had a number average degree of polymerization of n≈4.1 and a number average molecular weight of 1150. Example 3 In a reactor similar to that used in Example 1, 873 parts of dimethyl terephthalic acid, 94 parts of azelaic acid, and 1.4 parts of azelaic acid were added.
451 parts of butanediol and 204 parts of spiroglycol were charged, heated and melted, 0.03% tetrabutoxytitanium was added, and the temperature was raised to a final reaction temperature of 220°C.
The methanol produced was distilled off and the reaction was carried out. The obtained polyalkylene phthalate (A-3) showed crystallinity, and the measurement of the hydroxyl number showed that the resin was 1000%
The polyalkylene phthalate (A-3) had a number average molecular weight of 1155 and had a number average degree of polymerization n≈5.05 based on this value. Example 4 Synthesis of crystalline polyetherester elastomer: Using the same reactor as in Example 1, Examples 1-
(A) of the crystalline polyalkylene phthalate obtained in 3.
-1), (A-2), and (A-3) are reacted with polytetramethylene glycol in the compositions shown in the experiment numbers (a) to (e) listed in Table-1. a)～(e)
A crystalline polyetherester elastomer was obtained. For experiment numbers (a) to (d) listed in Table 1, the final reaction temperature was 220°C, and the resins were mainly dehydrated and esterified under reduced pressure to obtain the desired high molecular weight resins. On the other hand, for experiment number (e) listed in Table 1, the final reaction temperature
The temperature was set at 230°C, and the dediol reaction was mainly performed under reduced pressure to obtain the desired high molecular weight resin. The results of measuring each resin using the GPC (polystyrene equivalent value) method are also listed in Table 1. Further, the amount of modification of polytetramethylene glycol listed in Table 1 is a value estimated from the value determined from the amount of distilled water or glycol component.

[Table] Example 5 Preparation and evaluation results of adhesive composition: Using each elastomer obtained in Example 4 and having experiment numbers (a) to (e) listed in Table 2, the experiment numbers listed in Table 2 were used. Adhesive compositions were prepared by adding epoxy resins in the proportions shown in (1) to (10), and further adding a silane coupling agent for experiment numbers (5) to (10). For experiment numbers (1) to (5) in Table 2, each raw material was dissolved in a 1:1 mixed solvent of chloroform and tetrahydrofuran, coated on release paper, and dried under reduced pressure at 100°C. A film of 70±10 μm was obtained. In addition, for experiment numbers (6) to (8) in Table 2, an extruder with a screw diameter of 40 mmφ was used.
Extrusion 100±10μ through T-die at a temperature of ~180℃
A film of m was obtained. Also, experiment numbers (9) to (10) in Table-2
A solution with a solid content of 30% was prepared in a 1:1 mixed solvent of tricrene and dimethylformamide.

【table】

[Table] Tables 5 and 6 show the results of adhesion evaluations conducted on various adherends by the method described above using the adhesives of experiment numbers (1) to (10) listed in Table 4. . In the case of a solution-type adhesive, it was applied to the surface of the adherend in advance and then dried under reduced pressure at 100° C. for bonding. Each of the adherends listed in Tables 5 and 6 was bonded after degreasing with trichloride. In particular, those for which the adhesion test was conducted after sanding the surface of the adherend are indicated in Tables 5 and 6 with the letter S in the adhesion conditions section.

【table】

【table】

[Table] This adhesive is used to bond the pre-coated surfaces of the pre-coated steel sheets listed in Tables 5 and 6, using the same adhesive and the same bonding conditions. The average T-type peeling strength of the products tested in this state was in the range of 6 to 12 kg/inch, and the strength retention rate after 240 hours of hot water (40°C) immersion test was +80% or more. In addition, a test piece obtained using the same adhesive and the same bonding conditions was tested under a stress of 20 kg/cm ² at -20°C/40 minutes = +65°C/
The strength retention rate after 100 cycles of a 40-minute stress thermal cycle test was over 95%, and there was no creep phenomenon.

Claims (1)

[Scope of Claims] 1 (A) has a number average molecular weight in the range of 1 to 500,000 and has the general formula (However, R ₁ is a divalent group that remains after removing the hydroxyl group from an organic diol with a molecular weight of 303 or less,
R ₂ is the divalent group that remains after removing the carboxyl group from aromatic and aliphatic dicarboxylic acids with a molecular weight of 350 or less, and R ₃ is the terminal hydroxy group removed from polytetramethylene glycol with a number average molecular weight of 400 to 3000. It is a divalent group that remains after removal, and n represents a number average degree of polymerization in the range of 1 to 20. ) and 100 parts by weight of a crystalline block type thermoplastic elastomer which is a polyetherester elastomer represented by (B).
1. A structural adhesive composition comprising 1 to 40 parts by weight of an epoxy resin having at least 1.2 or more glycidyl groups in the molecule having a number average molecular weight of 450 or more and 30,000 or less. 2 Component (A) is obtained using dimethyl terephthalic acid or terephthalic acid as the dibasic acid component and one or more of ethylene glycol, 1,4-butanediol, and 1,6-hexanediol as the glycol component. A polyalkylene phthalate having a terminal methyl carboxyl group or a carboxyl group and a polytetramethylene glycol having a number average molecular weight of 500 to 2000 obtained by reacting with a number average molecular weight of 5 to 5.
200,000 polyetherester elastomer.