GB1596658A

GB1596658A - Fusion contact adhesives

Info

Publication number: GB1596658A
Application number: GB43550/77A
Authority: GB
Original assignee: Kores Holding Zug AG
Current assignee: Kores Holding Zug AG
Priority date: 1976-10-21
Filing date: 1977-10-19
Publication date: 1981-08-26
Also published as: FR2368526B1; IT1087073B; DE2649028A1; FR2368526A1; ATA782676A; AT348080B; DK468677A; ES463446A1

Description

(54) FUSION CONTACT ADHESIVES (71) We, KORES HOLDING ZUG AG, of Baarerstrasse 57, CH-6300 Zug, Switzerland, a Swiss Body Corporate, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to fusion contact adhesives.

Hitherto, pressure-sensitive adhesives have generally been applied from a solution or a dispersion in an organic solvent to a suitable support.

Recently, it has been recognised that it is possible, in the production of fusion contact adhesives, to dispense with the use of solvents for reasons of environmental hygiene. More particularly, injury to health, which occurs with the processing of adhesives dissolved or dispersed in organic solvents, and the danger of fire, are reasons why the procedure has been adopted of applying adhesives from a melt. Since the support material is often produced on a basis of synthetic plastics, danger of sparking occurs due to electrostatic charging, so that the organic solvents can easily be ignited.

An additional disadvantage found with solvent-containing adhesives, when applying them to the support, results from the fact that limits are set as regards the speed of production.

Accordingly, an attempt has recently been made to dispense with solvents and to work at higher temperatures in the fusion or melting range of the polymers. In this connection, however, a number of problems arise, which may or may not be acceptable, depending on the purpose of use, or which may have been only partially solved.

Usually, it is the lower resistance to oxidation and temperatureof the adhesive mixtures which causes problems, since relatively high temperatures are employed in the production of the fusion contact adhesives. More particularly the mastication procedure and the application itself require temperatures which are higher then 100"C. For the application of the fusion contact adhesives, suitable means of application have to be provided, but nevertheless the melt viscosity of the fusion contact adhesive must not be too high, since otherwise the difficulties which occur cannot be overcome.

In order to reduce the melt viscosity to values which facilitate the application of the adhesive a degree of polymerisation was usually chosen which was low and a relatively high proportion of plasticisers was added. As a result, however, the endurance strength of the fusion contact adhesive was lowered to such an extent that the adhesive could not withstand relatively strong stresses.

As a consequence, the said adhesives could only be used for certain purposes, such as for example for sticking objects which did not have to withstand any permanent stressing.

It has been attempted to produce fusion contact adhesives which are based on block copolymerisation of styrene and butadiene or of styrene and isoprene, with additions of modified or unmodified colophony or colophony esters, coumarone-indene resins, polyterpene resins, aliphatic diene-olefine hydrocarbon resins, polystyrene resins, mixed polymers of ethylene and vinyl acetate or polypropylene.

In accordance with other proposals, fusion contact adhesives have been tried which consisted of mixed polymers of vinyl esters with additions of waxes. The problem with these adhesives does however consist in that the endurance strength is too low.

The poor cohesion values with fusion contact adhesives produce endurance strengths of only a few minutes under a loading of 1.5 kg at 25"C and with a tape width of 1 cm.

Fusion contact adhesives which are based on ethylene-vinyl acetate copolymers and chlorinated hydrocarbons are only capable of very restricted use and hence they are used more particularly for the laying of carpets, in order to make the underside of the carpet non-slipping.

Tests carried out with fusion contact adhesives based on rubber have also been unsuccessful.

Consequently, it has not so far been possible to extend the field of use of fusion contact adhesives to include those areas where permanent loads occur, for example, in the packaging industry. There is a distinct marketing gap as regards packaging tapes.

It has been found, when devising the present invention, that it is useful to transform the thermoplastic structure of a polymer partially into a duroplastic structure in order to improve the endurance strength and the cold flow.

By means of the invention, it has been made possible to provide a fusion contact adhesive the endurance strength of which can be raised far above the values which existed with conventional fusion contact adhesives.

According to the invention a fusion contact adhesive is provided which comprises a copolymer of a polymeric phenolic and/or polymeric terpenephenolic component with one or more polymers which have been homogenized at a temperature of from 1300 to 1600C and are selected from butadiene-styrene polynmers, synthetic polyisoprene, natural rubber chloro-butyl rubber and ethylene-propylene polymers. It is believed that the reactive OH groups of the polymeric phenolic and/or terpenephenolic component form a crosslinked copolymerisate with the double bonds of the homogenized polymer reactant.

The proportion of the polymeric phenolic or terpenephenolic component in the copolymer may advantageously amount to up to 6% by weight and is preferably 0.01 to 3% by weight.

According to the invention, the copolymers may also be mixed with crosslinked polymers of the group consisting of butadiene-styrene polymers, synthetic polyisoprene. natural rubber, chlorobutyl rubber and ethylene-propylene polymers.

The polymeric phenolic or terpenephenolic component is of essential importance for the present invention. The degree of crosslinking is increased by the copolymerisation and as a result the endurance strength is improved. If a copolymer with terpenephenols is chosen, the adhesive nature of the fusion contact adhesive is also improved.

The polymeric phenolic or terpenephenolic component is essential for the present invention since firstly it provides a sufficient degree of crosslinking of the said polymers and secondly it prevents a too-strong curing action, which would lead to a loss of the adhesive properties of the fusion contact adhesive.

Another possible variation of the invention involves the production of mixtures of the copolymers with crosslinked polymers. If crosslinked polymers having a low degree of cross-linking are added, the adhesive properties of the adhesive are increased. On the other hand, with a higher degree of crosslinking, an additional improvement in the endurance strength is produced.

The fusion contact adhesives according to the invention are more especially suitable for adhesive tapes for which certain criteria as regards the properties of the adhesive have to be satisfied. In the first place, it is required that the adhesive tapes should adhere to a document or the like, but on the other hand the cohesion of the adhesive to the support has to be sufficient so as not to leave behind any residues on the stripping off of the adhesive tape. Thirdly, it is necessary that the adhesion forces of the adhesive with the support should be greater than with the document or like surface.

It is with the aid of the present invention that it has been possible to provide a suitable adhesive which meets all these conditions.

The properties of the adhesive may also be varied within certain limits by the method of application.

Accordingly, certain suitable methods have been developed, which will be briefly described hereinafter.

According to one such method one or more polymers of the group consisting of butadiene-styrene polymers, synthetic polyisoprene. natural rubber, chlorobutyl rubber and ethylene-propylene polymers are homogenised at a temperature of from 13ü C to 1600C, advantageously with kneading, and the polymeric phenolic or terpenephenolic component is added, as a result of which copolymerisation occurs, and the copolymer is applied to the support.

It is possible within the scope of the present invention for the polymeric phenolic or terpenephenolic component to be added during the homogenising procedure or following the latter.

It is also possible to add the polymeric phenolic or terpenephenolic component at a temperature which is lower than the copolymerisation temperature and thereafter to heat the mixture to the said copolymerisation temperature.

According to another method the polymeric phenolic or terpenephenolic component and thereafter one or more of the homogenized polymers, are applied to the support, whereupon copolymerisation takes place directly on the support.

Another possibility consists in that first of all the polymeric phenolic or terpenephenolic component is applied to the rear side of the support, whereupon the latter is coated on its front surface with the homogenized polymer. In this case, polymerisation only occurs with the reeling of the adhesive tape. However, this process can only be used when the polymeric phenolic or terpenephenolic component is able to diffuse or sublime in the adhesive.

The flexo-printing method, magnetic doctoring method, magnetic screen-printing method and intaglio printing method are suitable for the application of the adhesive.

It is also an important feature of the present invention that the polymeric phenolic or terpenephenolic component can be added both in the molten state and in a dissolved state or as a dispersion. In the two latter cases, organic solvents, more especially mineral oils, are suitable.

According to another modification of the present invention, the homogenised polymer or polymers is or are first of all applied to the support and the polymeric phenolic or terpenephenolic component or components is or are applied above said polymer(s). In this case also, copolymerisation occurs directly on the supporting tape.

A number of examples of polymeric phenolic components and also their characteristic data are given in the following table: Colophony modified phenol resin Characteristics: Melting point: 125"-135"C Colour No. (iodine colour no.) < 35 Acid no. 15-20 Viscosity (50% in toluene) at 20"C 70-130 cP Heat-hardenable cresol-resol Characteristics: Melting point: 55-60"C Viscosity (40% in ethyl glycol) at 20"C 80-110 cP Strongly base-reactive arylphenol resin Characteristics: Melting point 65-75"C Colour No. (iodine colour no.) < 250 Acid no. practically neutral Viscosity (50% in toluene) at 20"C 50-90 cP Base-reactive alkylphenol resin Characteristics:Melting point 60-75"C Colour No. (iodine colour no.) < 10 Acid no. practically neutral Viscosity (50% in toluene) at 20"C 40-50 cP Base-reactive alkyl phenol resin Characteristics: Melting point 50-70"C Colour No. (iodine colour no.) < 10 Acid no. practically neutral Viscosity (50% in toluene) at 20"C 25-40 cP Weakly base-reactive alkylphenol resin Characteristics:Melting point 50-60"C Colour No. (iodine colour No.) < 10 Acid no. practically neutral Viscosity (50% in toluene) at 20"C 15-30 cP Using copolymers of the polymeric phenolic compounds listed in the above table. it has been found possible to produce endurance strengths which are far greater than 10 minutes.

Suitable as support materials within the scope of the present invention are both synthetic plastics foils based on polypropylene, polyethylene and PVC, as well as Cellophane ("Cellophane is a Registered Trade Mark), paper, woven textile fabrics and the like.

If necessary, the supports can be provided with adhesive repelling back preparations. it also being possible, in accordance with one of the variants of the present invention for the polymeric phenolic or terpenephenolic component to be added to the back preparation.

WHAT WE CLAIM IS: 1. A fusion contact adhesive which comprises a copolymer of a polymeric phenolic and/or polymeric terpenephenolic component with one or more polymers which have been homogenized at a temperature of from 1300 to 1600C and are selected from butadiene styrene polymers, synthetic polyisoprene, natural rubber, chlorobutyl rubber and ethylene propylene polymers.

2. A fusion contact adhesive according to Claim 1, wherein the proportion of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. A number of examples of polymeric phenolic components and also their characteristic data are given in the following table: Colophony modified phenol resin Characteristics: Melting point: 125"-135"C Colour No. (iodine colour no.) < 35 Acid no. 15-20 Viscosity (50% in toluene) at 20"C 70-130 cP Heat-hardenable cresol-resol Characteristics: Melting point: 55-60"C Viscosity (40% in ethyl glycol) at 20"C 80-110 cP Strongly base-reactive arylphenol resin Characteristics: Melting point 65-75"C Colour No. (iodine colour no.) < 250 Acid no. practically neutral Viscosity (50% in toluene) at 20"C 50-90 cP Base-reactive alkylphenol resin Characteristics:Melting point 60-75"C Colour No. (iodine colour no.) < 10 Acid no. practically neutral Viscosity (50% in toluene) at 20"C 40-50 cP Base-reactive alkyl phenol resin Characteristics: Melting point 50-70"C Colour No. (iodine colour no.) < 10 Acid no. practically neutral Viscosity (50% in toluene) at 20"C 25-40 cP Weakly base-reactive alkylphenol resin Characteristics:Melting point 50-60"C Colour No. (iodine colour No.) < 10 Acid no. practically neutral Viscosity (50% in toluene) at 20"C 15-30 cP Using copolymers of the polymeric phenolic compounds listed in the above table. it has been found possible to produce endurance strengths which are far greater than 10 minutes. Suitable as support materials within the scope of the present invention are both synthetic plastics foils based on polypropylene, polyethylene and PVC, as well as Cellophane ("Cellophane is a Registered Trade Mark), paper, woven textile fabrics and the like. If necessary, the supports can be provided with adhesive repelling back preparations. it also being possible, in accordance with one of the variants of the present invention for the polymeric phenolic or terpenephenolic component to be added to the back preparation. WHAT WE CLAIM IS:

1. A fusion contact adhesive which comprises a copolymer of a polymeric phenolic and/or polymeric terpenephenolic component with one or more polymers which have been homogenized at a temperature of from 1300 to 1600C and are selected from butadiene styrene polymers, synthetic polyisoprene, natural rubber, chlorobutyl rubber and ethylene propylene polymers.

polymeric phenolic or terpenephenolic component in the copolymer amounts to up to 6% by weight.

3. A fusion contact adhesive according to Claim 1, wherein the proportion of the polymeric phenolic or terpenephenolic component is from 0.01 to 3% by weight.

4. A fusion contact adhesive according to Claim 1 or 2, wherein the copolymer is mixed with one or more crosslinked polymers selected from the group consisting of butadienestyrene polymers, synthetic polyisoprene, natural rubber, chlorobutyl rubber and ethylenepropylene polymers.

5. A fusion contact adhesive according to Claim 4, wherein the crosslinking is by oxygen, sulphur. nitrogen, urea, urethane or methylene bridges between the polymer chains.

6. A contact adhesive as claimed in Claim 1, substantially as herein described.

7. A method for applying a fusion contact adhesive as claimed in any of the preceding claims to a support, wherein one or more polymers selected from butadiene-styrene polymers, synthetic polyisoprene, natural rubber, chlorobutyl rubber and ethylenepropylene polymers are homogenised at a temperature of from 1300C to 1600C and the polymeric phenolic or terpenephenolic component is added, as a result of which copolymerization occurs, and the copolymer is applied to the support.

8. A method according to Claim 7, wherein the polymeric phenolic are terpenephenolic component is added to the polymer during the homogenisation.

9. A method according to Claim 7. wherein the polymer, after the homogenisation, is carried away through a discharge pipe in which the addition to it of the polymeric phenolic or terpenephenolic component takes place.

10. A method according to Claim 9, wherein the polymer is cooled in the discharge pipe to a temperature below the copolymerisation temperature, after which the polymeric phenolic or terpenephenolic component is added and the polymer is heated to copolymerisation temperature.

11. A method for applying a fusion contact adhesive as claimed in any of Claims 1 to 6 to a support. wherein the polymeric phenolic or terpenephenolic component and thereafter one or more polymers which have been homogenised at a temperature of from 1300 to 1600C and are selected from butadiene-styrene polymers, synthetic polyisoprene, natural rubber. chlorobutyl rubber and ethylene-propylene polymers, are applied to the support, whereupon copolymerisation takes place directly on the support.

12. A method according to Claim 11 wherein the polymeric phenolic or terpenephenolic component is applied to the back of the support.

13. A method for applying fusion contact adhesives according to any of Claims 1 to 6 to a support, wherein one or more of the polymers selected from butadiene-styrene polymers, synthetic polyisoprene, natural rubber, chlorobutyl rubber and ethylene-propylene polymers which have been homogenized at a temperature of from 130 to 16ü C, and thereafter the polymeric phenolic or terpenephenolic component or components, are applied to the support, whereupon copolymerisation takes place directly on the support.

14. A method according to any of the Claims 7 to 13, wherein homogenization is effected by kneading of the polymers.

15. A method according to any of Claims 7 to 14 wherein the polymeric phenolic or terpenephenolic component is employed in the form of a solution or dispersion in an organic solvent.

16. A method according to Claim 15. wherein the organic solvent is a mineral oil.

17. A method according to any of Claims 7 to 14, wherein the polymeric phenolic or terpenephenolic component is employed in a molten state.

18. A method as claimed in Claim 7, 12 or 13 for applying a fusion contact adhesive to a support, substantially as herein described.