JPH023433B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new polyester adhesive, and more specifically to a polyester adhesive that has excellent heat resistance and excellent adhesion to metals, particularly aluminum, steel, tin, etc. be. It has long been known that thermoplastic polyester resins have adhesive properties to metals, polyesters, and plastics such as polyvinyl chloride, and compared to thermoplastic adhesives such as ethylene and ethylene-vinyl acetate copolymers. Due to its excellent heat resistance, it has been attracting attention as an adhesive in recent years. However, due to their thermoplastic nature, the heat resistance of these thermoplastic resins is limited to the temperature at which the resin softens and flows, and if the bonded area is exposed to temperatures higher than that, the bond will break. Polyester resin, which is said to have excellent heat resistance, is no exception. For this reason, its range of application is limited to the field of non-structural adhesives that do not require heat-resistant adhesive properties. In order to improve the heat resistance and solvent resistance of thermoplastic polyester adhesives, attempts have been made to improve the heat resistance by adding a curing agent to cause a crosslinking reaction between polyester molecules. For example, a reaction between a carboxyl group or hydroxyl group in a polyester molecule and a compound having an epoxy group or an isocyanate group has been proposed. However, adhesives to which these curing agents are added have a drawback of poor stability during use and storage. That is, thermoplastic polyester adhesives are generally used in hot melt type or solution type; when used in hot melt type, they are heated to at least the melting temperature of the adhesive during application; In order to dry the solvent, it is heated at a temperature of around 100°C, for example, at which the solvent can evaporate, but even at such a relatively low temperature, the functional groups in the polyester molecule and the curing agent are Because the reaction progresses gradually, increasing viscosity or gelling, which affects adhesive performance, the adhesive must be applied and bonded in an extremely short period of time, which has the disadvantage of placing restrictions on equipment and work. have. It has also been proposed to use a polyisocyanate compound having a protected isocyanate group in a curing agent in order to improve the poor thermal stability and cause the reaction to occur at a desired temperature. This polyisocyanate compound is stable because its active isocyanate groups are protected by a specific compound, and there is no reaction activity with other functional groups; however, when heated above a specific temperature, the isocyanate group-protecting agent dissociates and becomes active. The resin is cured by producing isocyanate groups and causing a crosslinking reaction with the functional groups in the resin, and by selecting various protective agents, a heating temperature for heat curing can be obtained that suits the purpose. However, the reaction rate of such polyisocyanate compounds after dissociation of the protective agent is generally slower than that of polyisocyanate compounds having free isocyanate groups, and polyester resins that have excellent adhesion to metals, plastics, etc. In general, since the molecular weight is large, the amount of functional groups contained is small and the reaction rate is slow, so the curing time of the resin is long or it is not cured sufficiently, resulting in the disadvantage that the desired heat resistance cannot be obtained. It was hot. A long curing time is fatal in the joining process of structural members, and the product cannot be incorporated into the production line. As a measure to increase the curing speed, it has been proposed to use a polyester resin with a larger number of functional groups. In this case, both the hydroxyl group and the carboxyl group in the polyester molecule are reactive with isocyanate groups, but since the hydroxyl group is particularly reactive, it is preferable to increase the amount of hydroxyl groups, but linear polyester contains many hydroxyl groups in the molecular chain. Since it is difficult to inexpensively produce a resin with a high degree of polymerization, a method of increasing the amount of hydroxyl groups with a relatively low degree of polymerization is generally used. however,
Although such resins actually have a faster reaction rate and a shorter curing time, they have the disadvantage that the resin after curing becomes very brittle and the peel adhesion strength is significantly reduced. Therefore, there has been a strong desire for an adhesive that has excellent heat resistance and stability, short curing time, and excellent adhesive performance. As a result of various intensive studies aimed at providing an adhesive with the above-mentioned excellent performance, the present inventors discovered that a polyester resin with many hydroxyl groups, a high molecular weight polyester resin, and a protected It has been found that the desired objective can be achieved by blending the adhesive with a polyisocyanate compound having an isocyanate group in a specific ratio, and more surprisingly, the adhesive of the present invention can be applied to metals, particularly aluminum, steel and tin. The present invention was achieved based on the discovery that the adhesive has excellent adhesion performance. That is, the present invention comprises a polyester resin having a terminal hydroxyl group content of 10 to 95% by weight of 200 g equivalent/ton or more, and (B) an intrinsic viscosity [20% by weight in a mixed solvent of phenol:tetrachloroethane (1:1, weight ratio)]. Measured in °C, so on. 〕0.4 or more, terminal hydroxyl group content 200
Gram equivalent/ton of polyester resin 90~5
A polyester resin composition consisting of (C)
This is a thermosetting polyester adhesive prepared by blending a polyisocyanate compound having two or more protected isocyanate groups in one molecule in a proportion that satisfies the following formula. 10≧NCO/OH≧0.1 [However, NCO is the number of equivalents of isocyanate groups in the polyisocyanate compound, OH is the number of equivalents of the isocyanate group of the polyisocyanate compound, and OH is the number of equivalents of the (A) component and (B)
It represents the number of equivalents of terminal hydroxyl groups of the component polyester resin. ] The polyester resin of component (A), which is one component of the adhesive of the present invention, has a terminal hydroxyl group content of 200 g equivalent/ton or more. Such a polyester resin has an acid component consisting of at least one aromatic dicarboxylic acid, preferably at least one aromatic dicarboxylic acid and at least one saturated aliphatic dicarboxylic acid, particularly in a molar ratio of 70:30. and 100:0, and the alcohol component is a glycol, preferably at least two glycols, such as ethylene glycol and neopentyl glycol, especially in a molar ratio of
70:30 to 30:70 and 0 to 30 mol%, preferably 1 to 10 mol% of 3 to the glycol component.
Examples include those comprising an alcohol component having a higher alcohol content and having a terminal hydroxyl group content of 200 g equivalent/ton or more, preferably 250 g equivalent/ton or more. If the terminal hydroxyl group content is less than 200 g equivalent/ton, the reaction with the polyisocyanate compound will be slow, resulting in a longer curing time or insufficient curing, and as a result, the desired heat resistance will not be obtained. The polyester resin of component (B), which is one component of the adhesive of the present invention, has an intrinsic viscosity of 0.4 or more and a terminal hydroxyl group content of less than 200 g equivalent/ton. Such a polyester resin has an acid component consisting of at least one aromatic dicarboxylic acid, preferably at least one aromatic dicarboxylic acid and at least one saturated aliphatic dicarboxylic acid, particularly in a molar ratio of 50:50 to 50:50. 95:
5, the alcohol component is a glycol, preferably at least two glycols, such as ethylene glycol and neopentyl glycol,
In particular, those having a molar ratio of 70:30 to 30:70, an intrinsic viscosity of 0.4 or more, and a terminal hydroxyl group content of less than 200 gram equivalent/ton are mentioned. The intrinsic viscosity is
If it is less than 0.4, or if the terminal hydroxyl group content exceeds 200 gram equivalents/ton, the crosslinking reactivity will increase, and the adhesive will shrink more and lose its flexibility, resulting in poor adhesive performance. Examples of the aromatic dicarboxylic acids constituting the polyester resins of component (A) and component (B) include terephthalic acid, phthalic acid, and naphthalene dicarboxylic acid. Examples of aliphatic dicarboxylic acids include saturated aliphatic dicarboxylic acids having 4 to 20 carbon atoms, such as succinic acid, adipic acid, azelaic acid, and dodecanedioic acid. In addition, examples of glycol include ethylene glycol,
Alkylene glycols or poly(oxyalkylene) glycols such as trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, etc., and trihydric or higher alcohol components Examples include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, and the like. In the adhesive of the present invention, the blending ratio of component (A) and component (B) is 10:90 to 95:5 by weight, preferably
40:60 to 85:15. (A) The blending ratio of the ingredients is
If it is less than 10% by weight, it will be difficult to cure the adhesive and the heat resistance and adhesive performance will deteriorate;
If it exceeds % by weight, the adhesive after curing becomes brittle and loses its toughness, and its peel adhesive strength also decreases. The polyisocyanate compound of component (C), which is one component of the adhesive of the present invention, is a polyisocyanate compound having two or more protected isocyanate groups in one molecule. Such a polyisocyanate compound can be prepared using known methods such as adding a protective agent in an amount equivalent to the isocyanate group dropwise to an isocyanate compound, or adding an excess of a protective agent to an isocyanate compound and then removing the protective agent from the reaction system by distillation or extraction. It can be obtained by the following method. Examples of isocyanate compounds include tolylene diisocyanate, ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 4,4'-methylene-bis(cyclohexyl isocyanate), 4,4'-methylene-bis(phenyl isocyanate), ω, ω′-diisocyanate-1,3-dimethylbenzene, ω,
Examples include aromatic, aliphatic or ring group isocyanate compounds such as ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,3-dimethylcyclohexyl, isophorone diisocyanate, and triphenylmethane triisocyanate. . Examples of protective agents include blocking agents known to be used for blocking isocyanates, such as phenol-based, lactam-based, active methylene-based, alcohol-based, mercaptan-based, acid amide-based, imide-based, amine-based, imidazole type,
Any blocking agent such as urea, imine, oxime or sulfite may be used;
In particular, phenolic, oxime, lactam or active methylene blocking agents are advantageously used. Specific examples of blocking agents include phenolic blocking agents such as phenol, cresol, xylenol, and t-butylphenol, and lactam blocking agents such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam. Active methylene blocking agents include diethyl malonate, dimethyl malonate, ethyl acetoacetate, acetylacetone, etc. Alcohol blocking agents include methanol, ethanol, n-propyl alcohol, isobutyl alcohol, n-butyl alcohol, isobutyl alcohol, t- Butyl alcohol, ethylene glycol monoethyl ether, glycolic acid, methylol urea, methylol melamine, and oxime-based blocking agents include formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, and the like. The amount of polyisocyanate compound is NCO/
It is necessary that the OH equivalent ratio is in the range of 0.1-10, preferably 0.5-5. If the equivalence ratio is less than 0.1, curing will be difficult, while if the equivalence ratio is greater than 10, the adhesive cost will increase, and the amount of residual isocyanate groups will increase, causing adverse effects such as corrosion of the adhesive member. come. In the present invention, the adhesive can contain a known catalyst that accelerates the reaction rate of the polyisocyanate compound as component (C), and in this case, the curing time can be further shortened. Such catalysts include, for example, stannous diacetate, stannous di(ethylhexane), stannous tetraacetate, and tetra(2).
Examples include tin compounds such as stannic acid (ethylhexanoate), dibutyltin dilaurate, tetrabutyl-1,3-diformoxydistanoxane, and tetrabutyl-1,3-diacetoxydistanoxane. The preferred amount of catalyst used is about 0.1 to 10% relative to the polyisocyanate compound (C).
Weight%. The adhesive of the present invention can be used both as a solution adhesive and as a hot melt adhesive. When used as a solution type, industrial organic solvents such as benzene, toluene, acetone, chloroform, methylene chloride, ethyl acetate, cyclohexane, methyl ethyl ketone, phenol, etc. alone or in combination can be used as the solvent. The mixing order and dissolution method of the three components (A), (B), and (C) for manufacturing the adhesive are not particularly limited. For example, the three components are added to a stirring solvent tank, and then the solvent is mixed and dissolved. Manufactured by such methods as Furthermore, an appropriate amount of catalyst can be added as necessary. There are no particular restrictions on the order or method of mixing the three components when used as a hot melt adhesive, but when melt-mixing, the polyester resins (A) and (B) should melt and flow, and the (C) component should melt and flow. It is preferable to mix at a temperature range in which the protecting groups of the polyisocyanate compound do not dissociate. The preferred temperature range varies depending on the type of protective agent, etc., but is approximately 80 to
140°C, especially about 90-120°C. For such mixing, devices such as mixers, kneaders, hot roll mills, extruders, and Banbury mixers can be used. The simplest method for bonding two substrates using the adhesive of the invention thus obtained is to apply the adhesive of the invention onto one substrate, for example by spraying, brushing, roll coater, etc. In the case of a solution-type adhesive, the adhesive is applied by a method such as a doctor knife, and after the solvent is dried by heating, or in the case of a hot-melt adhesive, the other substrate is directly stacked on top of the other substrate, and then pressure is applied and heated. For adhesion, it is preferable to heat the adhesive at a temperature higher than the dissociation temperature of the protective agent of the polyisocyanate compound (component (C)) and apply pressure at the same time to bring the adhesive and the substrate into sufficient contact and hold it as is until it hardens. . Generally, this heating temperature is about 80-300℃, and the pressure is about 0.1-300℃.
It is 200Kg/ ^cm2 . This pressurization and heating process forms a strong bond between the adhesive and the substrate, and the adhesive itself is cross-linked and cured to generate high cohesive strength. The dressing of the present invention is formulated with two types of polyester resins, one with many functional groups and the other with high molecular weight and flexibility. The disadvantages of insufficient properties have been resolved, and the adhesive has the advantage of short curing time and excellent adhesive performance. Furthermore, the adhesive of the present invention is characterized by excellent heat resistance and stability during storage and use. In addition, the adhesive of the present invention has excellent adhesion to metals, especially aluminum, steel, tin, etc., and provides a bonding area with excellent heat resistance, so conventional thermoplastic copolyester resins It is possible to expand its use to the area of structural adhesives, which was previously impossible. Hereinafter, the present invention will be explained in more detail with reference to Examples. In addition, "parts" in the examples mean "parts by weight." Reference Example 1 [Manufacture of polyester resin (a)] 50 moles of dimethyl terephthalate, 40 moles of dimethyl isophthalate, 60 moles of ethylene glycol, 55 moles of neopentyl glycol, and 0.01 mole of zinc acetate as a catalyst were placed in a stainless steel reactor, and nitrogen was added. The transesterification reaction was carried out at 150-250°C under air flow. Next, 10 mol of adipic acid and 0.02 mol of antimony trioxide were added, and polycondensation was performed at 270°C under reduced pressure to produce a polymer. 5 mol of trimethylolpropane was added to this polymer and depolymerized at 280° C. under nitrogen pressure to obtain a polyester resin (a) having a terminal hydroxyl group content of 510 gram equivalents/ton. Reference Example 2 [Manufacture of polyester resin (b)] 65 mol of dimethyl terephthalate, 100 mol of ethylene glycol, 60 mol of neopentyl glycol, and 0.01 mol of zinc acetate as a catalyst were placed in a stainless steel reactor and heated at 50 to 250°C under a nitrogen stream. The transesterification reaction was carried out. Next, 35 moles of sebacic acid and 0.02 moles of antimony trioxide were added, and a polycondensation reaction was carried out at 270° C. under reduced pressure to obtain a polyester resin (b) having an intrinsic viscosity of 0.65 and a terminal hydroxyl group content of 130 g equivalent/ton. Examples 1 to 3, Comparative Examples 1 and 2 The polyester resin (a) of Reference Example 1 and the polyester resin (b) of Reference Example 2 were mixed at each compounding ratio shown in Table 1.
100 parts of this was taken and dissolved in 200 parts of a mixed solvent of toluene/methyl ethyl ketone (1:1, volume ratio) while heating at 60°C. After cooling the obtained solution to room temperature, add a toluylene diisocyanate-based compound protected with methyl ethyl ketoxium in an amount such that the amount of isocyanate groups is 1 in equivalent ratio to the hydroxyl groups contained in the polyester resins (a) and (b). Then, 0.1 part of dibutyltin dilaurate was added as a catalyst and dissolved to prepare an adhesive solution. For comparison, adhesives using polyester resin (a) or polyester resin (b) alone were also prepared in the same manner. These adhesive aluminum plates (thickness 1.6mm,
The adhesion performance and heat curing time for a width of 25 mm) were measured by the following method, and the results shown in Table 1 were obtained. () Tensile shear adhesive strength (Kg/cm ² ) Apply the adhesive solution prepared above to the metal piece for adhesion test using an applicator so that the thickness of the adhesive after drying is approximately 15 to 20 μm. After drying at ℃, another metal piece was attached to the surface coated with the above adhesive according to JISK-6580, and 1
Heat and press for 5 minutes at 180℃ under pressure of Kg/ ^cm2 ,
A test piece was prepared. Adhesive strength was measured using an Instron tensile tester at a tensile speed of 50 according to JISK-6850.
Tensile shear failure of the test piece was performed at 25°C and mm/min, and the strength was divided by the sheared area. () T-peel adhesive strength (Kg/25mm) Apply adhesive solution to the metal piece for adhesion test in the same way as for tensile shear adhesive strength measurement, dry it, and then apply another metal piece to JISK-6854. Therefore, they were pasted together and heat-pressed at 180° C. for 5 minutes under a pressure of 1 kg/cm ² to prepare a test piece. The adhesive strength is
In accordance with JISK-6854, the test piece was subjected to T-peeling under the same conditions as for tensile shear adhesive strength, and the strength was determined. () Heat curing time (minutes) A test piece was prepared in the same manner as the test piece for measuring tensile shear adhesive strength, and heat-pressed at 180°C for a predetermined time. A load of 300 g/cm ² per sheared area was applied to this test piece in an atmosphere of 180° C., and the heating time until the adhesive surface stopped flowing was determined, and this time was taken as the curing time of the adhesive.

[Table] Using the adhesive solutions of Example 1 and Comparative Example 2, tensile shear adhesive strength and T-peel adhesive strength were measured in the same manner as Example 1, using a steel plate with a thickness of 0.8 mm and a width of 25 mm as an adherend. The results shown in Table 2 were obtained.

[Table] In addition, using the adhesive solutions of Example 1 and Comparative Example 2, tensile shear adhesion and T-peel adhesion were measured using a tin plate with a thickness of 0.3 mm and a width of 25 mm as an adherend. Measurements were made in the same manner as in Example 1, and the results shown in Table 3 were obtained.

[Table] Reference example 3 [Manufacture of polyester resins (c), (d), and (e)] Addition of 5 mol of trimethylolpropane to 0,
Polyester resins (c), (d), and (v) were prepared in the same manner as in Reference Example 1 except that the hydroxyl group content was changed to (c) 155 gram equivalent/ton, (c) 155 gram equivalent/ton, ( Resins with (d) 261 gram equivalents/ton and (e) 982 gram equivalents/ton were obtained. Reference Example 4 [Manufacture of polyester resin (F)] To 100 moles of the polyester resin (B) produced in Reference Example 2, 2 moles of trimethylolpropane were added and depolymerized at 280°C under nitrogen pressure to contain terminal hydroxyl groups. A polyester resin (f) having an amount of 230 gram equivalents/ton and an intrinsic viscosity of 0.29 was obtained. Examples 4 and 5, Comparative Examples 3 and 4 As the polyester resin of component (A) and component (B),
Polyester resin (c) prepared in Reference Example 3 respectively
The procedure was the same as in Example 1 except that 70 parts of ~(e) and 30 parts of polyester resin (b) were used, or 70 parts of polyester resin (a) and 30 parts of polyester resin (f) prepared in Reference Example 4 were used. An adhesive solution was prepared, and then, in the same manner as in Example 1, the adhesive performance and heat curing time to an aluminum plate were measured. Table 4 shows the results.

[Table] Reference Example 5 A polyester resin (T) was prepared in the same manner as Reference Example 2 except that azelaic acid was added instead of sebacic acid, and the intrinsic viscosity was 0.60 and the terminal hydroxyl group content was
150 gram equivalents/ton of resin was obtained. Example 5 30 parts of the polyester resin (G) obtained in Reference Example 5 and 70 parts of the polyester resin (A) were melt-kneaded at 150° C. for 30 minutes in a Laboplast Mill (manufactured by Toyo Seiki Seisakusho). Thereafter, the temperature is lowered to 110° C., and methyl ethyl ketoxime-protected tolylene diisocyanate is added to the melt in an amount such that the NCO/OH equivalent ratio is 1, and 0.1 part of dibutyltin dilaurate may be added as a catalyst. It was melted and kneaded.
For the adhesion test, first, a sheet with a thickness of 0.2 mm was created from the molten mixture using a hot press molding machine at a molding temperature of 100°C, and this sheet was sandwiched between two aluminum plates with a thickness of 1.6 mm and a width of 25 mm in a sandwich shape. ,
Thermocompression bonding was carried out at 180° C. for 5 minutes under a pressure of 1 Kg/cm ² .
Adhesive performance was measured in the same manner as in Example 1. As a result, the tensile shear adhesive strength was 118 Kg/cm ² and the T-peel adhesive strength was 50 Kg/25 mm. Further, the heat curing time was 2 minutes.

Claims (1)

[Scope of Claims] 1 (A) 10 to 95% by weight of a polyester resin having a terminal hydroxyl group content of 200 g equivalent/ton or more, and (B) an intrinsic viscosity [phenol:tetrachloroethane (1:1,
Measured at 20℃ in a mixed solvent with a weight ratio of 0.4 or higher,
(C) A polyisocyanate compound having two or more protected isocyanate groups in one molecule is added to a polyester resin composition consisting of 90 to 5% by weight of a polyester resin having a terminal hydroxyl group content of less than 200 g equivalent/ton by the following formula. A thermosetting polyester adhesive that is formulated in a proportion that satisfies the following. 10≧NCO/OH≧0.1 [However, NCO is the number of equivalents of isocyanate groups in the polyisocyanate compound, OH is the number of equivalents of the isocyanate group of the polyisocyanate compound, and OH is the number of equivalents of the (A) component and (B)
It represents the number of equivalents of terminal hydroxyl groups of the component polyester resin. ]