Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
1999-07-13
2001-07-03
Chen, Vivian (Department: 1773)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S308000, C528S308600, C528S308700
Reexamination Certificate
active
06255443
ABSTRACT:
FIELD OF INVENTION
The present invention relates to thermoplastic copolyesters and copolyetheresters for hot-melt adhesive applications.
BACKGROUND OF THE INVENTION
The use of different copolyesters and copolyetheresters is described at length in the literature.
DE 196 32 473 and DE 196 32 474 describe fast crystallizing and highly-flexible copolyetherester hot-melt adhesives based on terephthalic acid, butane-1,4-diol, diethylene glycol, triethylene diol and polyethylene glycol. These copolyetheresters crystallize very fast at a melting point of over 115° C. The lower-melting polyesters, having a melting point of about 90° C., are not suitable for adhesive use as a film, web or powder due to their lower crystallization speed and the associated stickiness.
EP 698 648 describes low-melting copolyesters having a melting point of 60-130° C. for the hot-melt adhesive range. These polyesters are based on terephthalic acid, isophthalic acid, butane-1,4-diol, diethylene glycol and triethylene glycol. Ensuing from this monomer composition is the sole fact that the crystallization speed is far too low to justify the claims set forth in this document.
JP 59 011 383 describes polyesters for hot-melt PVC bonding adhesives having melting points of 80-160° C., comprising terephthalic acid, adipic acid, butane diol and diethylene glycol. This combination also yields an insufficient crystallization speed.
CH 618199 describes numerous copolyesters and their compositions, the copolyesters having melting points of 50-200° C. The crystallization behavior, however, is characterized as very slow.
Finally, U.S. Pat. No. 4,551,521 describes low-melting polyester adhesives having melting points of 60-130° C. These polyesters primarily comprise adipic acid and cyclohexane dimethanol, and readily fulfill the criterion of a high crystallization speed. In contrast to the polyesters and copolyetheresters of the present invention, however, the polyesters are completely aliphatic; in other words, no terephthalic acid is used. Completely-aliphatic polyesters have excellent biodegradability, but are therefore naturally susceptible to weather influences and moisture. This property is counterproductive for a hot-melt adhesive that is intended to connect two substrates and must possess a certain resistance to heat. According to the invention, the greater biodegradability is assured up to a 30% proportion of aromatic components.
All of the copolyesters or copolyetheresters described in the prior art are associated with significant drawbacks, and do not yield thermoplastic copolyester or copolyetherester hot-melt adhesive masses having the low melting point, high crystallization speed, high flexibility and chemical stability that would make them suitable for use as hot-melt adhesives in technical applications for difficult substrates.
Thus, a need exists for developing quick-crystallizing and lightly-flexible products, having maximum melting temperatures of 100° C., for hot-melt adhesive applications.
SUMMARY OF THE INVENTION
The invention is particularly oriented toward linear, low-melting, fast crystallizing and flexible copolyesters or copolyetheresters based on terephthalic acid, adipic acid, butane-1,4-diol, hexane-1,6-diol and, optionally, a long-chain, aliphatic component, such as polyethylene glycol, having an average molecular weight of 600 to 4000 g/mole or a dicarboxylic acid having an average molecular weight of 400 to 800 g/mole. Copolyesters containing components such as polyethylene glycol are no longer pure copolyesters, but instead copolyetheresters. The melting points of the described polyesters or copolyetheresters are in a range of 65-95° C.
These polyesters or polyetheresters serve as hot-melt adhesive masses for technical and textile applications in which temperature-sensitive substrates must be bonded.
The advantage of a low melting point, i.e. maximum of about 100° C., lies in the possibility of using lower application temperatures. This is most critical in the field of technical adhesives when substrates, such as PVC or polyolefins, are used, which have melting temperatures of less than 120° C. These low-melting polyester adhesives can also be used in the field of fusible interlinings if the substrates to be bonded are extremely temperature sensitive and tend to shrink, or even be destroyed, at excessive application temperatures.
The use of a copolyester or copolyetherester having a high crystallization speed is desirable for numerous reasons. The formation of crystalline regions is a prerequisite for the mechanical stability of a polymer above the glass-transition temperature. The faster these crystalline domains can form, the more mechanical stress the adhesion point can endure.
Furthermore, the surface stickiness of a polymer hot-melt adhesive is directly dependent on its crystallization. The lower the tendency toward crystallization, the longer the adhesive, e.g. in the form of films or adhesive nets, remain sticky. This poses problems when such films are rolled, for example, because the individual layers can stick to one another and render the entire roll unusable. This effect can be circumvented by the application of a so-called carrier film, which separates the applied adhesive from the next layer. Before the adhesive is pressed together with the further substrate, however, the film must be removed, which adds labor and, more importantly, increases waste. Another possibility is the use of time- and energy-consuming tempering procedures, which are naturally disadvantageous for the overall production process. The use of a fast-crystallizing polymer obviates all of these costly steps.
The advantages of highly-flexible products are clear. On the one hand, depending on the substrate, sufficient adhesive values and durability for adhesive connections in the field of technology can only be attained with flexible adhesive masses.
On the other hand, coated and bonded parts can be exposed at a later time to stresses and deformations, which cause conventional adhesives to lose their adhesive properties and lead to the detachment of substrates. In these cases, a highly-flexible adhesive is the only option for producing a permanent connection of materials.
It is therefore a principal object of the invention to reconcile the four required characteristics of “low melting point,” “high crystallization speed,” “high flexibility” and “high chemical stability” through the suitable combination of raw materials.
DETAILED DESCRIPTION OF THE INVENTION
The above object is accomplished by the low-melting, fast-crystallizing and highly-flexible copolyester or copolyetherester hot-melt adhesive masses comprising statistically-proportioned copolyesters or copolyetheresters based on terephthalic acid, adipic acid and a mixture of aliphatic diols, characterized in that the molar proportion of the acid components is 55 to 85 mole % of terephthalic acid, 15 to 40 mole % of adipic acid, and eventually 0 to 15 mole % of a long-chain, aliphatic dicarboxylic acid having a molar mass of 400 to 800 g/mole; the molar proportion of the diol components is 40 to 55 mole % of butane diol, 40 to 60 mole % of hexane diol, eventually 0 to 10% mole % of a long-chain, aliphatic diol having a molar mass of 600 to 4000 g/mole; and the melting point of the copolyester or copolyetherester hot-melt masses is 65-95° C.
The solution to the object lies especially in hot-melt adhesive masses comprising statistically-proportioned copolyesters and copolyetheresters, respectively, made up of a combination of butane diol (BD) and hexane diol (HD) and eventually other selected long-chain, linear, aliphatic diols and terephthalic acid (TPS) and adipic acid (ADI) and eventually other selected long-chain, aliphatic dicarboxylic acids as the acid components. The viscosity of these low-melting products is preferably less than 400 Pa*s at 160° C. to permit processing as a hot-melt at low temperatures.
In the use of terephthalic acid alone as the acid component, the melting points are generally far above the desired range. A reduction in the melting
Kinkelin Eberhard
Pössenecker Gerhard
Spindler Jurgen
Browdy and Neimark
Chen Vivian
EMS - Chemie AG
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