GB1594719A

GB1594719A - Fusible adhesives especially for the adhesion of textiles

Info

Publication number: GB1594719A
Application number: GB5349177A
Authority: GB
Original assignee: Schering AG
Current assignee: Bayer Pharma AG
Priority date: 1976-12-23
Filing date: 1977-12-22
Publication date: 1981-08-05
Also published as: IE46224L; IE46224B1; DE2658370A1; JPS6335187B2; JPS62252490A; DE2658370C2; JPS6157671A; JPS6338389B2; BE862277R

Description

(54) FUSIBLE ADHESIVES ESPECIALLY FOR THE ADHESION OF TEXTILES (71) We, SCHERING AKTIENGESELLSCHAFT, a body corporate organised according to the laws of the Federal Republic of Germany, of Berlin and Bergkamen, Federal Republic of Germany, 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 invention relates to polyamide fusible adhesives suitable for the adhesion of textiles to one another or to other materials.

The fusible adhesives based on dimeric fatty acid or caprolactam known hitherto do not fulfil satisfactorily practical requirements regarding properties and range of use.

This invention is an improvement in, or modification of, the invention of Patent No. 1,546,222 which describes and claims a process for adhesively uniting two surfaces, one of textile, siliconised fabric or rubber and the other of textile, siliconised fabric, rubber or leathter, which comprises applying a polyamide comprising units derivable from (a) a carboxylic acid component comprising (1) a dimerised fatty acid having a content of 70 to 100% by weight of dimeric fatty acid, (b) a dicarboxylic acid component comprising an aliphatic unbranched dicarb oxylic acid having from 6 to 13 carbon atoms, wherein the ratio of the carboxylic acid component (a) to dicarboxylic acid component (b) is from 0.05:1 to 5:1, calculated on carboxyl groups, (c) a diamine component comprising an aliphatic unbranched diprimary diamine having from 6 to 12 carbon atoms. and (d) caprolactam and/or -aminocaproic acid, to one or both of the surfaces and bringing the surfaces together, the polyamide being fused by the application of heat and pressure so that an adhesive bond is formed.

The carboxylic acid component (a) may, if desired, incluae (2) a monocarboxylic (monomeric) acid as viscosity regulator (chain breaker), wherein the total of monomeric acid in (al) and (a2) is no more than 50% of the total acid component, calculated on carboxyl groups.

Patent 1,546,222 also claims a composition for the preparation of a polyamide suitable as fusible adhesive, which comprises (a) a carboxylic acid component comprising (1) a dimerised fatty acid having a content of from 70 to 100% by weight of dimeric fatty acid or a polyamide-forming derivative thereof, (2) a monocarboxylic acid (monomeric) or a polyamide-forming derivative thereof, as chain breaker, wherein the total proportion of monomeric acid in components (al) and (a2), calculated as carboxyl equivalents, is more than 15% and up to 50%; (b) a dicarboxylic acid component comprising an aliphatic unbranched dicarb oxylic acid having from 6 to 13 carbon atoms, or a polyamide-forming derivative thereof, wherein the ratio of carboxylic acid component (a) to dicarboxylic acid component (b), calculated as carboxyl equivalents, is from 0.05:1 to 5:1; (c) a diamine component comprising an aliphatic unbranched diprimary diamine having from 6 to 12 carbon atoms, or a polyamide-forming derivative thereof, and (d) caprolactam and/or e-aminocaproic acid, and the polyamide prepared there from, and a process for adhesively uniting two surfaces each of textile, siliconised fabric leather or rubber, which comprises applying this polyamide to one or both of the surfaces and bringing the surfaces together, the polyamide being fused by the application of heat and pressure so that an adhesive bond is formed.

A melt-condensed polyamide interpolymer containing imine groups derived from (CrC2(,)polymethylene diamine and carbonyl groups derived from (C16-C10) dimerised fatty acid, (C6-C10 ) polymethylene diacid and (C,-C13 ) polymethylene omega-aminoacid is described in Patent 1,315,369.

We have found that in a preferred method of preparation of the polyamide used in the adhesion process of Patent 1,546,222, in a first stage the dimerised fatty acid (component (al)) is reacted with the total quantity or part of the caprolactam and/or of the -aminocaproic acid (component (d)), and in a second stage reaction is effected with the remainder of the composition. The block condensates thereby produced have improved water resistance.

We have also found that other satisfactory block condensates may be obtained if the caprolactam/r-aminocaproic acid component or part thereof is pre-condensed with one of the other acid components, e.g. the co-dicarboxylic acid (b) or acid (a2).

When the dimerised fatty acid component (al) is used for the pre-condensation, the components (al) and (a2) are usually pre-condensed together with the capro lactam/ie-aminocaproic acid. Alternatively, the chain breaker (a2) may be introduced later with the remaining components.

Accordingly, the present invention provides a process of adhesively uniting a textile, siliconised fabric leather or rubber substrate to the same, or a different, substrate in this group, which comprises applying a polyamide comprising units derived from (a) a carboxylic acid component comprising (1) a dimerised fatty acid having a content of 70 to 100% by weight of dimeric fatty acid or a polyamide-forming derivative thereof, (b) a dicarboxylic acid component comprising an aliphatic unbranched dicarb oxylic acid having from 6 to 13 carbon atoms, or a polyamide-forming derivative thereof, wherein the ratio of the carboxylic acid component (a) to carboxylic acid component (b) is from 0.05:1 to 5:1, calculated as carboxyl equivalents, (c) a diamine component comprising an aliphatic unbranched diprimary diamine having from 6 to 12 carbon atoms, or a polyamide-forming derivative thereof, and (d) caprolactam and/or e-aminocaproic acid, and which has been prepared by reacting, in a first stage, some or all of the acid constituent (a) and (b) with some or all of component (d), and, in a second stage, reacting the reaction product from the first stage with the remaining components, to the surface of one or both substrates, and bringing the surfaces together, the polyamide being fused so that an adhesive bond is formed.

The carboxylic acid component (a) may include (2) a monocarboxylic (monomeric) acid wherein the total proportion of monomeric acid in components (al) and (a2), calculated as carboxyl equivalents, is up to 50%.

The use of polyamides in which the carboxylic acid component (a) includes (2) a monocarboxylic (monomeric acid having from 12 to 22 carbon atoms, and preferably the weight of monomeric acid is up to 50% of the weight of the total mixture, should be mentioned. Thus some or all of (al), some or all of (a2) and/or some or all of (b) is used for the precondensation, especially some or all of components (al) and/or (b) and optionally (a2); e.g. the acid or acids of component (a) is/are first precondensed with some or all of component (d) and then reacted with the remaining components [(b) and (c) and, if any remain, (a) and (d)].

It should be understood that where appropriate one or more of the acids (al), (a2) and (b) may be present in the form of an ester or other polyamide-forming derivative, and references to carboxyl groups herein should be understood to include these ester or other groups. Similarly, an amine component (c) and aminocaporic acid (d) may each be in the form of a suitable polyamide-forming derivative.

Each component (al), (a2), (b), (c) and (d) may contain one or more of the substances specified thereunder.

According to the present invention the polyamides used as fusible adhesives, especially for textiles, advantageously have for this latter purpose a fusion viscosity (measured at 220"C) of from 25 to 600 Pa.s (Pascal seconds).

The fusible adhesives used according to the invention, which are built up on the basis of dimeric fatty acid, available in sufficient quantity, caprolactam or E-aminocaproic acid, diamines and co-dicarboxylic acids, have a good resistance to halogenated hydrocarbons and to washing liquors at 600C and, in the case of some of them, also at 95"C. This resistance is evidenced by 1. the very good initial tenacities, that is before being subjected to stress by the washing or cleaning process.

2. the very high wet tenacities, that is after cleaning and when still in the damp state, and 3. the excellent tear resistance values after drying which are almost completely retained after many washing or cleaning cycles.

When a distilled dimeric fatty acid is used, a fusible adhesive with an improved colour number may be obtained. On the other hand, industrial polymerised fatty acid may also be used for producing fusible adhesives for special purposes. However, when using industrial dimeric fatty acid it is necessary to ensure that the content of trimeric fatty acid does not exceed a maximum limit. This limiting value depends on the content of dimeric and monomeric fatty acid in the polymerised fatty acid and can be determined by an orientating test such as is part of the daily routine of the average man skilled in the art.

The term "dimerised fatty acid" is used herein in a general sense to denote polymerised acids obtained from fatty acids. Thus, the dimerised fatty acid component may consist. only of dimeric acid or may comprise the dimeric acid and optionally the monomeric and/or higher polymeric, primarily trimeric, acid. The term "fatty acid" includes unsaturated natural and synthetic monobasic aliphatic acids having from 12 to 22 carbon atoms, preferably 18 carbon atoms. These fatty acids can be polymerised by known processes (cf. German Offenlegungschriften 1,443,938 and 1,443,968 and German Patent Specifications 2,118,702 and 1,280,852).

Typical polymeric fatty acids available commercially have approximately the following composition: Monomeric acids (Mo) 5-15 per cent by weight dimeric acids (Di) 60-80 per cent by weight trimeric acids (Tri) 10-15 per cent by weight The content of dimeric acid may be increased to up to 100% by weight by known methods of distillation.

Preferably the fatty acid component (al) has a content of dimeric fatty acid of at least 90% by weight. More especially, there are used dimerised fatty acids containing more than 90% of dimeric fatty acid and small amounts of trimeric fatty acid (2 to 6% by weight) and monomeric fatty acid (0 to 1.5% by weight); dimerised fatty acids generally obtainable commercially are suitable.

It is also possible to use a saturated dimerised fatty acid or one of the above dimerised fatty acids in hydrogenated form.

The polyamides used according to the invention come within a specific range of fusion viscosities, usually 25-600 Pa.s (measured at 2206C), especially 25-150 Pa.s, which reflects a specific molecular weight range.

The fusion viscosity may be adjusted in known manner by breaking off the reaction at the desired degree of polymerisation or by working with non-equivalent quantities of carboxylic acids or amines. Because of certain disadvantages in these methods it is preferable to use monofunctional or monofunctionally-acting amines and/or carboxylic acids as chain breakers. Monocarboxylic acids have proved to be especially favourable.

The proportion of monocarboxylic (monomeric) acid in the polymerised fatty acid used according to the invention may be increased by the addition of monocarboxylic acids (a2) to up to 50 equivalents %, calculated on total carboxyl groups of the mixture of polymeric fatty acid and monomeric monocarboxylic acid. If the proportion of the necessary chain-breaker (viscosity regulator), in this case the monocarboxylic acid, is high, monocarboxylic acids of higher molecular weight (hydro phobic chain breakers) are preferably used. Examples are oleic, stearic, linoleic or linolenic acid or mixtures thereof, e.g. tall oil fatty acid or soya oil fatty acid, and other hydrophobic monocarboxylic acids.

For example, the acid of both components (al) and (a2) may have from 12 to 22 carbon atoms. Especially there may be used a commercially available dimerised fatty acid and additional fatty acid in its monomeric form, or a dimerised fatty acid having more than 15 equivalents % of monomeric monocarboxylic acid, and, if desired, additional chain breaker component (a2).

The present invention also provides a polyamide comprising units derived from (a) a carboxylic acid component comprising (1) a dimerised fatty acid having a content of from 70 to 100% by weight of dimeric fatty acid, or a polyamide-forming derivative thereof, and (2) a monocarboxylic acid (monomeric) or a polyamide-forming derivative thereof, as chain breaker, wherein the total proportion of monomeric acid in component (al) and (a2), calculated as carboxyl equivalents, is up to 50%, and preferably more than 15%, (b) a dicarboxylic acid component comprising an aliphatic unbranched dicarb oxylic acid having from 6 to 13 carbon atoms, or a polyamide-forming derivative thereof, wherein the ratio of carboxylic acid component (a) to dicarboxylic acid component (b), calculated as carbonyl equivalents, is from 0.05:1 to 5:1, (c) a diamine component comprising an aliphatic unbranched diprimary diamine having from 6 to 12 carbon atoms, or a polyamide-forming derivative thereof, and (d) caprolactam and/or E-aminocaproic acid, and which has been prepaied by reacting, in a first stage, some or all of the acid constituent (a) and (b) with some or all of component (d), and, in a second stage, reacting the reaction product from the first stage with the remaining components.

The present invention also provides a process for the preparation of a polyamide of the present invention which comprises reacting some or all of the acid constituent (a) and (b) specified above with some or all of component (d) specified above and subsequently reacting with the remaining components.

Suitable aliphatic unbranched co-dicarboxylic acids having from 6 to 13 carbqn atoms (component (b)) are, for example, adipic acid, nonamethylene dicarboxylic acid, decamethylene dicarboxylic acid and brassylic acid. Sebacic acid is preferred.

The dicarboxylic acids may be used singly or in admixture.

Optionally, instead of the carboxylic acids, esters th.ereof with lower aliphatic alcohols may be used. In this case, especially when the proportion of ester is high, it is recommended to initiate the caprolactam polymerisation by the addition of water.

Preferably the ratio of component (a) to component (b) is from 0.1:1 to 3:1 Suitable aliphatic unbranched diprimary diamines having from 6 to 12 carbon atoms (component (c)) are, for examyle, 1,6-diaminohexane, 1,9-diaminononane and 1,12-diaminododecane. 1,6-diaminohexane is preferred.

As is known in the art, in the preparation of the polyamide the amount of component (c) should generally be substantially equivalent to the amount of acid constituent (i.e. components '(a) and (b)).

The quantity of caprolactam/s-aminocaproic acid used, calculated on mols of carboxyl groups of the acids used, depends on the melting point desired. Usually this should be no more than 140"C. Thus, for fusible polyamide textile adhesives 0.5 to 1.5 mol of lactam and/or -aminocaproic acid per mol of carboxyl groups is preferred.

More especially 0.8 to 1.2 mol of component (d) are used per mol of carboxyl groups of components (a) and (b).

Suitable materials for adhesively uniting are textiles, and also siliconised fabrics which may be adhesively joined to one another, or to leather, rubber or other materials.

According to the present invention the polyamides may be used together with one or more other additives commonly used in the textile field, e.g. lubricants for improving the trickling ability of textile adhesive powders, plasticisers, optical brighteners and/or antioxidants.

According to one variant of a process of the present invention, fatty acid (component (al)) or an amide-forming derivative thereof is condensed in the first stage optionally together with component (a2) with some or all of the caprolactam and/or E-aminocaproic acid. In doing this, a low temperature is preferably used initially (i.e. approximately 1500C) so that the reaction is easy to control. At the end of the reaction the temperature is increased to the necessary level. The ratios of the reactants in this first stage vary according to the desired degree of addition of aminocaproic acid or caprolactam. In the second stage the other necessary constituents are added to the reaction product and the reaction is completed in the manner customary for amide production.

Solvents or diluents may be used to facilitate the reaction.

According to the invention the fusion viscosity of the polyamide should preferably be from 25 to 600 Pa.s, measured at 220"C.

The following Examples illustrate the invention, the polymerised fatty acids being used in the following respective Examples being as follows: Examples 1, 4 and 6. dimerised tall oil fatty acid having the following composition: monomeric fatty acid 3.6% by weight dimeric fatty acid 94.2% by weight trimeric fatty acid 2.2% by weight Examples 2 and 3. dimerised oleic acid of the following composition: monomeric fatty acid 5.3% by weight dimeric fatty acid 93.3% by weight trimeric fatty acid 1.4% by weight Example 5. dimerised soya oil fatty acid of the following composition: monomeric fatty acid 11.2% by weight dimeric fatty acid 76.3% by weight trimeric fatty acid 12.5% by weight In each Example tests were carried out as follows: Determination of the softening point The determination was carried out on a Kofler hot block in the following manner: The finely ground polyamide powder having a particle size from 0.3 to 0.5 mm was strewn on to the Kofler hot block. Then a small sheet of paper was pressed on to the softening region and after 90 seconds was removed slowly from tbe colder side of the block. At a certain temperature polyamide filaments form between the block and the paper being withdrawn. This temperature limit is considered to be the softening point.

Production of the adhesive joins.

Strips of fabric of polyester/wool (55%/45%)- 5 cm wide were adhesively joined. The polyamide powder had a particle size of 300 to 500 ,. The quantity applied was 20 grams per square metre of fabric.

The coated strips of fabric were adhesively united at temperatures of about 20 to 30 degrees C above the softening point of the polyamide adhesive to a second uncoated strip of fabric. The time taken to cause adhesion was about 15 to 20 seconds and the adhesion pressure was 400 grams per cm2.

Separation-resistance tests.

The test portions of fabric were subjected, wet, at room temnerature to a separation-resistance test according to DIN 53274. The width of the test portion was, however, 5 cm.

Washing and cleaning process.

Washing was carried out with a 3% strength washing liquor of a commercial machine detergent at temperatures of 60"C and 950C. The washing process at 600C lasted for 45 minutes, and at 950C for 90 minutes. The washing programme included a rinsing and centrifuging operation.

The resulting test portions of fabric were subiected, wet, at room temperature to a separation-resistance test according to DIN 53274. The width of the test portion was, however, 5 cm.

Chemical cleaning was carried out with perchioroethylene for 30 minutes at room temperature. The cleaned test portions of fabric were again tested wet.

Example 1.

22.23 k of dimerised tall oil fattv acid and 14.81 kg of tall oil fatty acid were heated to 250"C under nitrogen with 146.90 kg of canrolactam in a reactor provided with a stirrer, a descending condenser and a thermometer. The mixture was left at this temperature for four hours. 131.40 kg of sebacic acid and 143.00 kg of 1,12-diaminododecane were added to the acid thus obtained, and the whole was condensed out for four hours at 250"C. For the last two hours a vacuum of 2 mm mercury was applied.

Tests were performed on the polyamide as described above.

The polyamide had the following values: Softening point: 131"C Fusion viscosity at 2200C: 154.0 Pa.s Separation resistance (i) initial value: 5.7 kp/5 cm (ii) after washing at 600C: 3.5 kp/5 cm (torn wet) (iii) after perchloroethylene 4.1 kp/5 cm (torn wet) cleaning: The polyamides given in the following Table were prepared in the same manner.

TABLE 1 Ratio of the carboxyl Mol of (d) per mol Example Composition groups of (a) : (b) of carboxyl groups 2 171.46 g dimerised oleic acid 1.0: 1.0 1.0 10.94'g soya oil fatty acid 23.3i g adipic acid 30.32 g azelaic acid 74.43 g 1,6-diaminohexane 144.64 g caprolactam 3 139.50 g dimerised tall oil fatty acid 0.5 1.0 0.67 2.85 g tall oil fatty acid 136.00 g dimethyl brassylate 87.71 g 1,6-diaminohexane 113.08 g caprolactam 4 228.00 g dimerised tall oil fatty acid 4.0: 1.0 1.3 20.22 g sebacic acid 58.17 g 1,6-hexamethylenediamine 146.19 g caprolactam 5 78.75 g dimerised tall oil fatty acid 0.5 : 1.0 1.0 7.78 g tall oil fatty acid 61.38 g sebacic acid 52.94 g 1,6-diaminohexane 102.96 g caprolactam TABLE 2

Separation resistance (kp/5 cm) Fusion viscosity 60 C wash Perchloroethylene torn wet Example Softening point at 220 C (Pa.s) Initial values cleaning torn wet 2 122 C 48.0 5.1 3.0 3.2 3 128 C 231.5 5.3 3.5 3.3 4 112 C 191.0 5.8 3.7 2.6 5 103 C 527.0 7.7 3.5 4.5 Example 6 Polyamide Pre-condensation of caprolactam with co-dicarboxylic acid (b) Ratio of Mol of(d) per mol Composition (a) : (b) of carboxyl groups 141.51 g sebacic acid 0.1 : 1.0 1 : 1.14 197.75 g caprolactam 25.14 g dimerised tall oil fatty acid (94.2% strength) 14.76 g stearic acid 89.53 g 1,6-diaminohexane

Separation resistance (kp/5 cm) Fusion viscosity Perchloroethylene Softening point at 220 C (Pa.s) Initial value 60 C wash 95 C wash cleaning torn wet 122 C 101 5.9 4.0 3.8 5.5

Claims

WHAT WE CLAIM IS:-

1. A process of adhesively uniting a textile, siliconised fabric, leather or rubber substrate to the same, or a different, substrate in this list, which comprises applying a polyamide comprising units derived from (a) a carboxylic acid component comprising (1) a dimerised fatty acid having a content of 70 to 100% by weight of dimeric fatty acid, or a polyamide-forming derivative thereof, (b) a dicarboxylic acid component comprising an aliphatic unbranched dicarb oxylic acid having from 6 to 13 carbon atoms, or a polyamide-forming derivative thereof, wherein the ratio of the carboxylic acid component (a) to carboxylic acid component (b) is from 0.05:1 to 5:1, calculated as carboxyl equivalents (c) a diamine component comprising an aliphatic unbranched diprimary diamine having from 6 to 12 carbon atoms, or a polyamide-forming derivative thereof, and (d) caprolactam and/or -aminocaproic acid, and which has been prepared by reacting, in a first stage, some or all of the acid constituent (a) and (b) with some or all of component (d) and, in a second stage, reacting the product with the remaining components, to a surface of one or both sub strates and bringing the surfaces together, the polyamide being fused by the application of heat and pressure so that an adhesive bond is formed.

2. A process of adhesively unting a textile, siliconised fabric, leather or rubber substrate to the same, or a different, substrate in this list, which comprises applying a polyamide comprising units derived from (a) a carboxylic acid component comprising (1) a dimerised fatty acid having a content of from 70 to 100% by weight of dimeric fatty acid or a polyamide-forming derivative thereof, and (2) a monocarboxylic acid (monomeric) or a polyamide-forming derivative thereof, as chain breaker, wherein the total proportion of monomeric acid in components (al) and (a2), calculated as carboxyl equivalents, is up to 50%.

(b) a dicarboxylic acid component comprising an aliphatic unbranched dicarb oxylic acid having from 6 to 13 carbon atoms, or a polyamide-forming derivative thereof, wherein the ratio of carboxylic acid component (a) to dicarboxylic acid component (b), calculated as carboxyl equivalents, is from 0.05:1 to 5:1, (c) a diamine component comprising an aliphatic unbranched diprimary diamine having from 6 to 12 carbon atoms, or a polyamide-forming derivative thereof, and (d) caprolactam and/or E-aminocaproic acid, and which has been prepared by reacting, in a first stage, some or all of the acid constituent (a) and (b) with some or all of component (d) and, in a second stage, reacting the product with the remaining components, to a surface of one or both substrates and bringing the surfaces together, the polyamide being fused by the application of heat and pressure so that an adhesive bond is formed.

3. A process as claimed in claim 2, wherein the monocarboxylic acid (component (a2)) has from 12 to 22 carbon atoms.

4. A process as claimed in claim 3, wherein component (a2) comprises oleic, stearic, linoleic or linolenic acid, tall oil fatty acid or soya oil fatty acid.

5. A process as claimed in any one of claims 2 to 4, wherein the total proportion of monomeric acid in components (al) and (a2), calculated as carboxyl equivalents, is more than 15%.

6. A process as claimed in any one of claims 1 to 5, wherein in preparing the polyamide some or all of component (al) is used in the first stage and components (b) and (c) and, if any remain, (d) and (al) in the second stage, component (a2) if used being added at either stage.

7. A process as claimed in claim 6, wherein all of component (al) is used in the first stage.

8. A process as claimed in claim 7, wherein all of component (a2) is added in the first stage.

9. A process as claimed in claim 3 or claim 4, wherein in preparing the polyamide all of component (al) and (a2) is used in the first stage.

10. A process as claimed in any one of claims 1 to 5, wherein in preparing the polyamide some or all of component (b) is used in the first stage and components (al), (a2) (if used), and (c) and, if any remain, (d) and (b) in the second stage.

11. A process as claimed in any one of claims 2 to 5, wherein in preparing the polyamide some or all of component (a2) is used in the first stage and ,components (al), (c) and, if any remain, (a2) and (d) in the second stage.

12. A process as claimed in any one of claims 1 to 11, wherein the amount of component (d) is from 0.5 to 1.5 mols per mol of carboxyl groups of components (a) and (b).

13. A process as claimed in claim 9, wherein the amount of component (d) is from 0.5 to 1.5 mols per mol of carboxyl groups of components (a) and (b).

14. A process as daimed in claim 12 or claim 13, wherein the amount of component (d) is from 0.8 to 1.2 mols per mol of carboxyl groups of components (a) and (b).

15. A process as claimed in any one of claims 1 to 14, wherein component (al) contains at least 90% by weight of dimeric fatty acid.

16. A process as claimed in claim 15, wherein component (al) contains from 2 to 6% by weight of trimeric fatty acid and from 0 to 1.5% by weight of monomeric fatty acid.

17. A process as claimed in any one of claims 1 to 16, wherein the fatty acid of component (al) is an unsaturated natural or synthetic monobasic acid having 18 carbon atoms.

18. A process as claimed in claim 17, wherein component (al) is dimerised tall oil fatty acid, oleic acid, soya oil fatty acid, stearic, linoleic or linojenic acid.

19. A process as claimed in any one of claims 1 to 18, wherein the ratio of carboxylic acid component (a) to dicarboxylic acid component (b), calculated as carboxyl equivalents, is from 0.1:1 to 3:1.

20. A process as claimed in any one of claims 1 to I, wherein component (b) comprises sebacic acid, adipic acid, nonamethylene dicarboxylic acid, decamethylene dicarboxylic acid or brassylic acid or a mixture of two or more such compounds.

21. A process as claimed in claim 20, wherein component (b) is sebacic acid.

22. A process as claimed in any one of claims 1 to 21, wherein component (c) comprises hexamethylenediamine, 1,9-diaminononane or 1,12-diaminododecane or a mixture of two or more such compounds.

23. A process as claimed in claim 22, wherein component (c) is hexamethylenediamine.

24. A process as claimed in claim 1, wherein the polyamide is, and has been prepared, substantially as described in any one of the Examples 1 to 5 herein.

25. A process as claimed in claim 1, wherein the polyamide is, and has been prepared, substantially as described in Example 6 herein.

26. A process as claimed in any one of claims 1 to 25, wherein the polyamide has a fusion viscosity of from 25 to 600 Pa.s, measured at 220"C.

27. A process as claimed in any one of claims 1 to 26, wherein the polyamide is applied in the form of a fusible adhesive composition containing an additive comprising a lubricant, plasticiser, optical brightener, or antioxidant or a mixture of two or more such additives.

28. Substrates which have been united by a process as claimed in any one of claims 1 to 27.

29. A polyamide comprising units derived from (a) a carboxylic acid component comprising (1) a dimerised fatty acid having a content of from 70 to 100% by weight of dimeric fatty acid or a polyamide-forming derivative thereof, and (2) a monocarboxylic acid (monomeric) or a polyamide forming derivative thereof, as chain breaker, wherein the total proportion of monomeric acid in components (al) and (a2), calculated as carboxyl equivalents, is up to 50%; (b) a dicarboxylic acid component comprising an aliphatic unbranched dicarb oxylic acid having from 6 to 13 carbon atoms, or a polyamide-forming derivative thereof, wherein the ratio of carboxylic acid component (a) to dicarboxylic acid component (b), calculated as carboxyl equivalents, is from 0.05:1 to 5:1; (c) a diamine component comprising an aliphatic unbranched diprimary diamine having from 6 to 12 carbon atoms, or a polyamide-forming derivative thereof, and (d) caprolactam and/or -aminocaproic acid, and which has been prepared by reacting, in a first stage, some or all of the acid constituent (a) and (b) with some or all of component (d) and, in a second stage, reacting the product with th,e remaining components.

30. A polyamide as claimed in claim 29, wherein the monocarboxylic acid (component (a2)) has from 12 to 22 carbon atoms.

31. A polyamide as claimed in claim 30, wherein component (a2) comprises oleic, stearic, linoleic or linolenic acid, tall oil fatty acid or soya oil fatty acid.

32. A polyamide as claimed in any one of claims 29 to 31, wherein the total proportion of monomeric acid in components (al) and (a2), calculated as carboxyl equivalents, is more than 15%.

33. A polyamide as claimed in any one of claims 29 to 32, wherein some or all of component (al) is used in the first stage-and components (b) and (c) and, if any remain, (d) and (al) in the second stage, component (a2) being added at either stage.

34. A polyamide as claimed in claim 33, wherein all of component (al) is used in the first stage.

35. A polyamide as claimed in claim 34, wherein all of component (a2) is added in the first stage.

36. A polyamide as claimed in claim 30 or claim 31, wherein all of component (al) and (a2) is used in the first stage.

37. A polyamide as claimed in any one of claims 29 to 32, wherein some orfi all of component (b) is used in the first stage and components (al), (a2), and (c) and, if any remain, (d) and (b) in the second stage.

38. A polyamide as claimed in any one of claims 29 to 32, wherein some or all of component (a2) is used in the first stage, and component (al), (c) and, if any remain, (a2) and (d) in the second stage.

39. A polyamide as claimed in any one of claims 29 to 38, wherein the amount of component (d) is from 0.5 to 1.5 mols per mol of carboxyl groups of components (a) and (b).

40. A polyamide as claimed in claim 39, wherein the amount of component (d) is from 0.5 to 1.5 mols per mol of carboxyl groups of components (a) and (b).

41. A polyamide as claimed in claim 39 or claim 40, wherein the amount of component (d) is from 0.8 to 1.2 mols per mol of carboxyl groups of components (a) and (b).

42. A polyamide as claimed in any one of claims 39 to 41, wherein component (al) contains at least 90% by weight of dimeric fatty acid.

43. A polyamide as claimed in claim 42, wherein component (al) contains from 2 to 6% by weight of trimeric fatty acid and from 0 to 1.5% by weight of monomeric fatty acid.

44. A polyamide as claimed in any one of claims 39 to 43, wherein the fatty acid of component (al) is an unsaturated natural or synthetic monobasic acid having 18 carbon atoms.

45. A polyamide as claimed in claim 44, wherein component (awl) is dimerised tall oil fatty acid, oleic acid, soya oil fatty acid, stearic, linoleic or linolenic acid.

46. A polyamide as claimed in any one of claims 29 to 45, wherein the ratio of carboxylic acid component (a) to dicarboxylic acid component (b), calculated as carboxyl equivalents, is from 0.1:1 to 3:1.

47. A polyamide as claimed in any one of claims 29 to 46, wherein component (b) comprises sebacic acid, adipic acid, nonamethylene dicarboxylic acid decamethylene dicarboxylic acid or brassylic acid or a mixture of two or more such compounds.

48. A polyamide as claimed in claim 47, wherein component (b) is sebacic acid.

49. A polyamide as claimed in any one of claims 29 to 48, wherein component (c) comprises hexamethylenediamine, 1,9-diaminononane or 1,12-diaminododecane or a mixture of two or more such compounds.

50. A polyamide as claimed in claim 49, wherein component (c) is hexamethylenediamine.

51. A polyamide as claimed in claim 29, which is, and which has been prepared, substantially as described in any one of the Examples 1 to 4 herein.

52. A polyamide as claimed in claim 29, which is, and which has been prepared, substantially as described in Example 6 herein.

53. A process for the preparation of a polyamide as claimed in claim 29 which comprises reacting some or all of the acid constituents ((a) and (b)) with some or all of component (d) and subsequently reacting with the remaining components.

54. A process as claimed in claim 53, carried out substantially as described in any one of the Examples 1 to 4 herein

55. A process as claimed in claim 53, carried out substantially as described in Example 6 herein.

56. A polyamide as claimed in claim 29, whenever prepared by a process as claimed in any one of claims 53 to 55.

57. A polyamide as claimed in any one of claims 29 to 52 and 56, which has a fusion viscosity of from 25 to 600 Pa.s, measured at 220"C.

58. A fusible adhesive composition suitable for textiles, which comprises a polyamide as claimed in any one of claims 29 to 52 and 56 and an additive comprising a lubricant, plasticiser, optical brightener or antioxidant or a mixture of two or more such addditives.