JPH01299883A - Hot melt adhesive - Google Patents

Abstract

PURPOSE:To obtain the title adhesive excellent in peeling strength and heat resistance, by forming a polyester of a specified composition by reacting a dicarboxylic acid component comprising terephthalic acid and an aliphatic dicarboxylic acid with a diol component comprising 1,4butanediol and 1,9- nonanediol or 2-methyl-1,8-octanediol. CONSTITUTION:A dicarboxylic acid component comprising terephthalic acid and a 6-36C aliphatic dicarboxylic acid (e.g., adipic acid) is reacted with a diol comprising 1,4-butanediol and 1,9-nonanediol or 2-methyl-1,8-octanediol to obtain a polyester composed of a dicarboxylic acid component comprising 45-85mol% terephthalic acid residues (a) and 15-55mol% aliphatic dicarboxylic acid residues (b) and a diol component comprising 30-80mol% 1,4-butanediol residues (c) and 20-70mol% 1,9-nonanediol residues or 2-methyl-1,8-octanediol residues (d) and having a total content of (b) and (d) of 40-100mol%, a glass transition point <=-10 deg.C and an m.p. of 80-160 deg.C.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is directed to plastic films, especially polyethylene film.
The present invention relates to a hot melt adhesive that has superior peel strength and heat resistance to phthalate (PET) film.

<Prior art> Polyester hot melt adhesives have good heat resistance, weather resistance, solvent resistance, and electrical properties, so they are widely used for product assemblies such as electrical products and automobiles. It has become. As the composition of such an adhesive, it is well known that the composition is a copolymerization of an acid component mainly consisting of terephthalic acid residues and 1,4-aliphatic dicarboxylic acid or glycols. However, in general, those with relatively high crystallinity have excellent shear adhesion and heat resistance, but have low peel adhesion, and lower crystallinity increases peel adhesion, but vice versa. However, it has the disadvantage of reduced heat resistance.

By the way, plastic films typified by PET films have been widely used for packaging, magnetic tapes, and the like. Furthermore, in recent years, applications have expanded to include bonding films together via intermediate laminates such as flexible printed circuit boards and surface heating elements, and sealing molded objects made of plastic such as lids for food containers. There is. Hot-melt adhesives are preferred from the viewpoint of improved hygiene and productivity, but among these, polyester-based adhesives are attracting attention because PET film is often used as the base film. (Adhesion 28 (8) 347 (1984)). The required performance for such uses is, of course, high peel adhesion strength at room temperature, but in addition to this, heat-resistant adhesive strength is also often required. However, as mentioned above, none of the copolymer volier and stell type hot melt adhesives proposed so far has satisfied both requirements. In contrast, a polyether-2 ester elastomer, which is copolymerized with a large amount of polyalkylene ether glycol, has been proposed as an adhesive with an excellent balance of peel strength and heat resistance. Therefore, it has not been put into practical use due to poor thermal stability, applicator suitability, and water resistance.

Therefore, it has been desired to develop a polyester hot melt adhesive that has high peel adhesion to plastic films from room temperature to high temperatures, and has excellent thermal stability, suitability for applicators, and hot water resistance.

Means for Solving the Problems As a result of intensive studies aimed at providing a copolyester hot melt adhesive that solves the above problems, the inventors have found that various aliphatic dicarboxylic acids as comonomers have been used as comonomers. The present inventors have discovered that the desired objective can be achieved by combining a specific glycol, more preferably a small amount of polyalkylene ether glycol, and have completed the present invention. That is, the present invention provides (a) 45 to 85 mol% of terephthalic acid residues and (b) 6 to 36 carbon atoms.
a dicarboxylic acid component consisting of 15 to 55 mol% of aliphatic dicarboxylic acid residues, (c) 30 to 80 mol% of 1,4-butanediol residues, and (d) 1,9-nonanediol residues or 2-methyl - Consists of 20 to 70 mol% of 1,8-octanediol residues, the sum of the above (b) and (d) is 40 to Ii mol%, and has a glass transition point measured by differential scanning calorimeter (DSC). This hot-melt adhesive is suitable for use in plastic films, and is made of polyester as a main component and has a temperature of 110°C or less and a melting point of 80 to 160°C.

The copolymerized polyester in the present invention is characterized by a polybutylene terephthalate polyester mainly containing a terephthalic acid component and a 1,4-butanediol component, an aliphatic dicarboxylic acid component, and a 1,9-nonanediol component or 2
-Methyl-1,8-octanediol component is used in a specific amount. The above-mentioned polyester has a feature that the amount of crystalline range per unit volume can be reduced even though it has a relatively high melting point and a relatively low glass transition point without using a long chain glycol such as polyalkylene glycol. Therefore, a polymer having a relatively high melting point and a low elastic modulus near room temperature can be obtained, and therefore it is possible to exhibit the desired high peel adhesion strength from room temperature to high temperature. Furthermore, the addition of a small amount of polyalkylene ether glycol, which does not improve peel strength with conventional polyester without impairing heat resistance and water resistance, improves peel adhesion, and especially peel adhesion due to changes over time after adhesion. A polyester hot melt adhesive with little loss of strength is obtained.

Terephthalic acid, which is an aromatic dicarboxylic acid component constituting the adhesive of the present invention, contributes to raising the softening point of the resin and imparting heat resistance, and its composition ratio is 45 to 8% of the acid component.
5 mol%, preferably in the range of 60 to 75 mol%.

When the proportion of the terephthalic acid component is less than 45 mol %, the heat-resistant peel adhesive strength decreases, while when it exceeds 85 mol %, the room temperature peel adhesive strength decreases. Also, aliphatic dicarboxylic acid and 1,9-nonanediol or 2-methyl-1,8
- Octanediol lowers the Tg of the resin and increases the volume fraction of the amorphous region, so it contributes to imparting high peel adhesion. The amount of the aliphatic dicarboxylic acid component is 15 to 55 mol%, preferably 25 to 40 mol% of the total acid component, and 1,9-nonanediol or 2-methyl-1,
The amount of 8-octanediol component is 2 in the total glycol component.
0 to 70 mol%, preferably 30 to 50 mol%, and the sum of the amounts of both components (b) and (d) is 40 to 70 mol%.
It is 100 mol%, preferably 45 to 80 mol%. If the sum of both components is less than 40 mol%, the peel adhesive strength at room temperature will be low, while if it exceeds 100 mol%, the heat-resistant peel strength will decrease.

Furthermore, when polyalkylene ether glycol is copolymerized with the above composition, the peel adhesion strength at room temperature or below increases,
Further, it is possible to reduce the decrease in adhesive strength over the entire temperature range due to changes over time. In this case, the amount of polyalkylene glycol can be up to 20% by weight based on the total polymer.

If it exceeds this, the properties as a hot melt adhesive will be impaired.

Furthermore, monomers commonly used in copolyesters, such as isophthalic acid, phthalic acid, ethylene glycol, and neopentyl glycol, can be copolymerized within a range that does not impair the properties of the resin.

The above polyester resin has an intrinsic viscosity [η] of 0.5 or more,
It is preferably 1.5 or less. If the intrinsic viscosity is too low, it will be difficult to maintain strong adhesive properties, while if it is too high, the adhesive properties will be reduced.

As for the thermal properties of the resin of the present invention, the glass transition point (Tg) measured by DSC is -1θ°C or lower, preferably -20°C or lower, and the melting point (Tn) is in the range of 80 to 160°C.

In addition, the polymer was once melted by DSC, and the temperature was 100°C/f.
It is preferable that the heat of crystal fusion (ΔH) measured during heating at 10° C./min after cooling at f1 in is 23 J/G or less. If the glass transition point exceeds 110° C. or higher and the melting point exceeds 160° C. or higher, the peel adhesive strength at room temperature will decrease, while if the melting point is lower than 80° C., the heat-resistant peel adhesive strength will decrease. It does not matter how low the glass transition point is, but a polymer with a very low glass transition point will have a low melting point, resulting in a decrease in heat-resistant peel adhesive strength. Furthermore, if the heat of crystal fusion is too large, the peel adhesion strength at room temperature will decrease.

The aliphatic dicarboxylic acid that is a component of the copolymerized polyester in the present invention has 6 to 36 carbon atoms, such as adipic acid, azelaic acid, cepacic acid, decanedicarboxylic acid, icosandicarboxylic acid, and dimer acid. I can do it.

Examples of polyalkylene ether glycol include those having an average molecular weight of about 350 to 6000, preferably about 600 to 4000, such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhebutamethylene glycol, and polyoctamethylene glycol. , polynonamethylene glycol, etc. can be used.

The method for producing the copolymerized polyester in the present invention is not particularly limited, and can be carried out in accordance with known ordinary methods. For example, the aromatic film dicarboxylic acid component,
Aliphatic dicarboxylic acid component, 1,4-butanediol, 1
．． It is possible to adopt a method in which 9-nonanediol is directly esterified simultaneously or in stages, or it is transesterified and then polymerized. Furthermore, ester-forming derivatives such as lower alkyl and allyl esters can also be used as the acid component. Any known catalysts, stabilizers, modifiers or additives may be used during the polymerization or transesterification reaction.

The hot melt adhesive of the present invention can be used in exactly the same way as a general hot melt adhesive.

For example, the hot melt adhesive of the present invention can be applied in a molten state to an adherend using a general hot melt applicator or roll coater, or can be dissolved in a solvent and applied to an adherend by solution coating. You can also. Further, after being formed into a tape, film, powder, fiber, non-woven fabric, etc. by any forming method, it can be sandwiched between or laminated on an adherend for use. Furthermore, since the hot melt adhesive of the present invention is thermoplastic, it can also be laminated by coextrusion with other adherend films or sheets. The laminate obtained above can be heated to a temperature equal to or higher than the softening point and fused to an adherend, if necessary.

The hot melt adhesive of the present invention can be used by adding and mixing known additives and other resin materials to the above-mentioned polyester, if necessary. Examples of additives include inorganic particles such as silica, talc, and titanium oxide, antioxidants, and ultraviolet absorbers. Also, known resins that can be mixed include vinyl chloride resin, polystyrene resin,
Examples include polyester resin, epoxy resin, urethane resin, and the like.

Adherents to which the hot melt adhesive of the present invention is preferably applicable are plastics. In particular, it is preferable that the adherend is a film or sheet mainly composed of polyethylene terephthalate. Although it is particularly suitable for bonding PET films together, as long as at least one of the adherends is P-ET, the other adherends are not limited. For example, adhesion between PET film and metals such as aluminum, etc.
It can also be bonded to plastics such as soft polyvinyl chloride and hard polyvinyl chloride, urethane foam, etc.

(Example) A more specific explanation will be given below using an example. In addition, in the following examples, various physical property values were determined by the following measurement method.

(a) Intrinsic viscosity [η]: Measured at 30'C using a mixed solvent of phenol/tetrachloroethane (1/1: weight ratio).

(b) T-peel adhesive strength: A hot melt adhesive is sandwiched between two 75 μm thick biaxially stretched PET films,
A PET/adhesive adhesive/PE layer film was prepared by hot pressing at 150°C, 10 kg/cn+ for 2 minutes. The thickness of the adhesive layer at this time is IO(Lp
It is ra. Then, the T-peel adhesive strength at a predetermined temperature was measured at a peel rate of 20 mm/min according to JIs K6854.

(°C) Melting point (TIll), heat of crystal fusion (ΔH) and glass transition point (Tg): DSCTA3000 manufactured by Mettler
Using the system, 10 mg of sample was used, and the sample was once melted and rapidly cooled at 100° C./min, and then measured by increasing the temperature at a heating rate of 10° C./min. T11 and ΔH were determined from the peak temperature and peak area of the crystal melting peak. In addition, Tg is determined by the polymer measurement method (polymer measurement method, Baifukan (1)
973)) It was determined from the temperature at the midpoint (C) of the transition region by the method described in 181P.

Example 1 65 mol of dimethyl terephthalate, 35 mol of adipic acid,
1,4-butanediol 115 mol, nonanediol 2
2.5 mol, 22.5 mol of 2-methyl-1,l1l-octanediol and 0.0 mol of tetraisopropoxy titanate.
02 mol was added as a catalyst and heated at 200℃1 under nitrogen atmosphere.
The mixture was further heated at 220° C. for 30 minutes to carry out a transesterification reaction. Next, polycondensation was carried out by heating at 260°C for 3 hours under vacuum to form a copolymerized polyester (intrinsic viscosity 0.76 g/dL).
(melting point: 102°C). Table 1 shows the temperature dependence of the PET/PET T-peel adhesive strength and the polymer physical properties when this polymer is used.

Example 2.3 and Comparative Examples 1 to 3 Copolymerized polyesters were obtained using the same polymerization method as in Example 1, but with different compositions of the acid component and glycol component. Furthermore, the PET/PET adhesive strength was evaluated in the same manner as in Example 1. The results are shown in Table 1 as in Example 1.

Below is a blank space Example 4 The reaction was carried out in exactly the same manner as in Example 1 up to the transesterification reaction, and then 2 moles of polytetramethylene glycol was added and then polycondensed by heating at 260°C under vacuum for 3 hours, as shown in Table 1. A copolymerized polyester having a blocky composition was obtained. Table 1 shows the PET/PET adhesive strength as in the Examples and Comparative Examples.

Further, the change over time in the peel adhesive strength after adhesion was measured after being left at 20° C. for 1 day and 30 days, and compared with Example 2, as shown in FIG. It can be seen that the change in adhesive strength over time is improved by copolymerizing polytetramethylene glycol.

Example 5 The copolymerized polyester obtained in Example 4 was sandwiched between a 400μ thick soft PVC sheet and various adherends, and heated at 120°C for 1 hour.
A laminate of PVC/adhesive/various adherends was produced by hot pressing at 0 kg/cab' for 30 seconds. The thickness of the adhesive at this time is looμ. Then JIS
According to K6854, 1800 peeling at 20"C was measured at a peeling rate of 100 rats/min. The results are shown in Table 2, and the hot melt adhesive of this example showed good performance not only with PET but also with other adherends. Shows adhesion.

Table 2 <Effects of the invention> As is clear from the above explanation, various aliphatic acids and 1.9
-Using a specified amount of nonanediol or 2-methyl-1°8-octanediol, and increasing the glass transition temperature to 11
It can be seen that the copolymerized polyester having a composition of 0° C. or lower has superior T-peel adhesion to PET film over a wide temperature range (particularly on the high temperature side) than those using aliphatic acid alone or in combination with isophthalic acid. In addition, by copolymerizing a small amount of polyalkylene ether glycol to the above composition, it is possible to further reduce the change in adhesive strength over time, which is a common drawback of crystalline adhesives, without impairing the properties of the hot melt adhesive. can.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the change over time in the peel adhesive strength of the hot melt adhesive of the present invention. Patent applicant: RiRa Co., Ltd. Agent: Ken Honda, patent attorney

Claims (4)

[Claims] (1) (a) 45 to 85 mol% of terephthalic acid residues and (
b) C6-36 aliphatic dicarboxylic acid residue 15-5
dicarboxylic acid component consisting of 5 mol% and (c) 1,4-
butanediol residue 30-80 mol% and (d) 1,9
- composed of a diol component consisting of 20 to 70 mol% of nonanediol residue or 2-methyl-1,8-octanediol, and the sum of (b) and (d) is 40 to 100%.
mol%, the glass transition point measured by differential scanning calorimeter (DSC) is -10°C or less, and the melting point is 80 to 1
A hot melt adhesive whose main component is polyester at a temperature of 60°C. (2) In addition to the composition described in claim 1, the average molecular weight is 360.
A hot melt adhesive whose main component is a polyester copolymerized with 20% by weight or less of polyalkylene ether glycol residues. (3) A laminate of the polyester layer and plastic according to claim 1 or 2. (4) Claim 3, wherein the plastic is in the form of a film.
The laminate described in .