CA1091838A

CA1091838A - Hot-melt adhesive based on a saturated polyester

Info

Publication number: CA1091838A
Application number: CA294,690A
Authority: CA
Inventors: Hans G. Matthies; Ludwig Beer; Lothar Maempel
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1977-01-28
Filing date: 1978-01-10
Publication date: 1980-12-16
Also published as: FR2378838A1; DE2703417A1; IT1104144B; FR2378838B1; IT7847804A0; JPS5396043A; GB1593340A

Abstract

ABSTRACT OF THE DISCLOSURE:
A hot-melt adhesive, comprising a polyester obtained from 10-40 mole % of adipic acid, 60-90 mole % of terephthalic acid and an alkanediol of 2 to 6 carbon atoms, and containing a) from 0.05 to 0.5 per cent by weight, based on the polyester, of talc and b) from 0.05 to 0.5 per cent by weight, based on the polyester, of an ester or salt of a phosphorus oxyacid.
The hot-melt adhesive may be used particularly advantageously for bonding leather.

Description

:109i838 -Z~ 3~,402 ~OT-~LT ADHESrVE BASED ON A SATU~ATED POLYESTER

Thermoplastic polymers, eg. polyvinyl compounds, synthetic nylons and saturated linear copolyesters are ircre~sir.g'y employ~d as hot-melt adhesives.
Linear, saturated copolyesters based on aromatic and/or ali-phatic dicarboxylic acids and aliphatlc glycols have been disclosed, particularly for bonding leather, imitation leather and similar materials. ~or example, such hot-melt adhesives are described in U.S. Patent 3,090,772, British Patent 813,212, Belgian Patents 557,309 and 747,199 and French Patent 1,179,399. ~urthermore, it has lon~ been known in the art that the rate of crystallization Pnd hence the rate of solidification can be increased substantially oy addin~ an i~organic fine powder which is virtually insoluole in the pol~mers.
The copolyesters hitherto employed industrially as hot-melt adhes1ves consist either o~ at least 4 components or of mixtures of different copolyesters, and their -rate of solidification in general is UnSatiS~aCtOr~J. Because of the relatively complicated starting mixtures, such copolyesters are in general not readily obtainable with a sufficiently high degree o~ polymerization by using conventional polyester-manufacturing equipment and the properties of the products are not always sufficiently reproducible.

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1091~3~ 0.Z. 32,402 A further disadvantage of the conventional hot-melt adhesives based on sat~rated polyesters is that they have poor strength, ie. a low adhesion coupled with a lo~ elongation at break cf the bonds. Furthermore, the conventional hot-melt adhesives bæsed on saturated polyesters exhibit undesirable discoloration.
We have found that ho-melt adhesives comprising a polyester obtained from 10-40 mole ~ of adipic acid, 60-90 mole ~ of tereph-thalic acid and an alkanediol of 2-6 carbon atoms, which contain (a) from 0.05 to 0.5 per cent by weight, based on the polyester, o talc and (b) from 0.05 to 0.5 per cent by weight, based on the polyester, of an ester or salt of a phosphorus ox~acid, exhibit particularly good strength and virtually no tendenc~r to d~scslor.
A further advantage of the new hot-melt ~dhesives is that they can readily be produced with a suf~icientl~J hlgh degree of pol~Jconden-sation in conventlonal polyester-manufacturing equipment. The poly-esters used for the new hot-melt adhesives preferably contain, as condensed units, from 20 to 35 mole ~ of adipic acid and from 80 to 65 mole % o~ terephthalic acid, to~ether with linear alkanediols of 2 to 6 carbon atoms which possess terminal 0~ groups. Polyesters which contain 1,4-butanediol as the alkanediol are of particular interest, but examples of other suitable alkanediols are 1,2-ethyl-ene glycol, 1,3-propanediol and 1,6-hexanediol.
The polyesters can be manufactured in the conventional manner by polycondensation, ie. by reacting the dicarboxylic acids or their derivatives, for example their dial~yl esters with lower alcohols, in particular their methyl esters, with alkansdiols in the presence of conventional catalysts and in general have an intrinsic viscosity of from o.36 to 1.93, especialiy lrom 0.53 to 0.9~, measured in an 0.5~ strength solution in a mixture of o-j 30 dichlorobenzene and phenol, in a weight rat-o of 2:~, at 25C. The polyesters can also be manufactured in the conventional manner 'C-J

-2-109~83~ o . z . ~2,402 co-polycondensing the alkanediol esters of terephthalic acid with adiplc acld.
The talc contalned ln the novel hot-melt adhesives may be added to the polyester durlng or after the polycondensatlon and prefer-ably has a partlcle size of less than 10/um, especially of from 1 to 5/um .
Examples o~ derlvatives of phosphorus oxyaclds contained in the hot-melt adhesives are alkali metal salts and ammonium salts of phosphoric acid and of phosphorous acid, eg. sodium dihydrogen phosphate, sodium dihydrogen phosphite, ammonium dihydrogen phosphate and trlmethylammonlum dihydrogen phosphate, as well as alkali metal salts, especially sodlum salts, of polyphosphoric acids (for example Cal~on). Particularl~ suitable esters of phosphorlc acids are phosphites and phosphates of aliphatic and/or aromatlc alcohols or, preferably, of phenols. Specific examples are triphenyl phosphite, triphenyl phosphate, tris-nonylphenyl phosphite, tris-dodecylphenyl phosphite, tris-undecylphenyl phosphite,tris-non~ylphenyl phosphate, triisopropylphenyl phosphite, tris-tertiary butylphenyl phosphite and esters of alkanols which in most cases are of 1 to ~ carbon atoms, eg. trimethyl phosphate, phenyl diethyl phosphite, dlbutyl phenyl ~ phosphite, dicyclohexyl hydrogen phosphite and also diphenyl ethyl ^~ phosphate, and glycol phosphate. Phenol esters of phosphorous acid, in particular triphenyl phosphite, are of special interest.
Polyesters which have been manufactured using an alkyl titanate, ~- especially tetrabutyl orthotitanate, as the catalyst in the conven-tional manner have proved particularly suitable for the manufactur~
of the hot-melt adhesives. The novel adhesives may in particular ~^ be used for bonding leather and can be employed with advantage in shoe manufacture.
In the Example which follows, parts are by wei~ht.

-3-~09i~338 . z. ~i2, 402 EXAMPLE
g7 parts of dimethyl terephthalate and 68 parts of 1,4-butane-diol are heated to 140C, whilst stirring, in a heated stirred ; kettle fitted with a column. 0.1 part of tetrabutyl orthotitanateis gradually introduced into the homogeneous melt and the tempera-ture of the reaction mixture is raised to 230C in the course of 2 hours, whilst stirring. The methanol liberated is distilled off - through the column. After completion of the trans-esterification, 22 parts of adipic acid are introduced into the melt, whilst stirr-ing at 2~0 under atmospheric pressure, and the mixture ls stirred 10 until the calculated amount o~ ~Jater has been removed. 0.1 part of triphenyl phosphite and 0.1 part of talc (parti¢le size 10/um) are then added to the batch; the melt i~ heated ln the course of one hour to 245-250C, whilst stirring and at the same time reduc-lng the pressure to below 1 mm Hg, and post-condensation is continued, at the stated temperature, until the deslred degree of pol~Jconden-sation is reached, which requires ~rom about 2 to 3 hours. A color-less polycondensate having an intrinsic viscosity of 0.73 (measured in an 0.5~ strength solution in a 2:~ mixture of o-dichlorobenzene s and phenol at ~5C) and a melting point, determined by differential 20 thermoanalysis, of 175C, is obtained.
A film 0.5 mm thick is for~.ed from the hot-melt adnesive obtained and its mechanical properties are determined. The follo~Jin~
values are found:
flexural strength 22 N/mm2 ~ ,~
elongation at break 90%
lexing resistance 1,~00 (90 flexing angle; the number of flexin~ cJcles required to break the speci-men is rreasured~
, ., COMPARATI~JE EXPERIr~l~MT
, ., `. ~0 IN ACCORDANCE '.IrITX 3ELGIAN PATEiNT 747,199 155 parts of dimethyl terephthalate, ~8.8 parts of isophtnalic 109~83~ Z- ~2,402 acid, 1~5 parts of 1,4-butanediol, 7.44 x 10 3 part of zinc acetate and 15.5 x 10 ~ part of tetrabutyl orthotitanate are introduced into a hested stirred kettle fltted with a column, and are heated at 180-220C whilst stlrrin~ under nitrogen. The methanol liberated ls distilled o~f throu2h the column. 0.2 part o~` triphenyl phos-phite and 0.2 part of talc (particle size 10/um) ~re then added, the temperature is brought to 250C, and is then raised in the course of one hour to 270C whllst reducing the pressure to 1 mm Hg.
Stirring is then continued for about 1 hour under these conditions, until the desired degree of polycondensation is reached. A polyester having an intrinsic viscosity of 0.7~ (measured in a 2:3 mixture of o-dlchlorobenzene and phenol at 25C) is obtained.
A film 0.5 mm thick is formed from the molten product and its mechanical properties are determined. The following values are found:
flexural strength ~ 5 N/mm elongation at break < 5~
flexing resistance 1 (breaks after first flexing cycle) (90 flexing angle; the number of flexing cycles required to break the specimen is measured).

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Claims

We claim:

1. A hot-melt adhesive comprising a polyester obtained from 10-40 mole % (based an acid component) of adipic acid, 60-90 mole %
(based an acid component) of terephthalic acid and an alkanediolof 2 to 6 carbon atoms, and containing a) from 0.05 to 0.5 per cent by weight, based on the polyester, of talc and b) from 0.05 to 0.5 per cent by weight, based on the polyester, of an ester or salt of a phosphorus oxyacid.

2. A hot-melt adhesive as claimed in claim 1, which contains a phenol ester of phosphorous acid as component (b).

3. A hot-melt adhesive as claimed in claim 1,which contains triphenyl phosphite as component (b).