CH624970A5 - Process for the preparation of glass-transparent polyamide - Google Patents

Description

624 970

2nd

PATENT CLAIM Process for the production of crystal-clear, transparent polyamide, characterized in that a reaction mixture consisting of a) diamine of the formula I

^ h y— nh2 (i)

n in the R 1 and R 2 independently of one another are each hydrogen or the methyl group, and n is 0-6,

and the hydrogen atoms of the two cyclohexane rings can be partially or completely replaced by methyl groups,

b) polyamide-forming dicarboxylic acid, which consists of 85 to 100 mol% of isophthalic acid or a mixture of isophthalic and terephthalic acid, the molar ratio of terephthalic acid: isophthalic acid being at most 1: 1 in the latter case, and c) one component , consisting of ci) an oh amino acid or its lactam with more than 9 carbon atoms, or c2) a salt or mixture of equimolar amounts of an aliphatic dicarboxylic acid and a diprimeric aliphatic diamine,

polycondensed, with component c) the condition that the average number of methylene groups between the polyamide-forming functions is at least 9, and component ti) additionally the condition that the number of methylene groups between the polyamide-forming functions neither with the dicarboxylic acid nor with Diamine is less than 6, is satisfied, component c) including any aliphatic dicarboxylic acid belonging to component b) makes up 30 to 40% of the total weight of components a), b) and c) and the molar amounts of components a) and b) are about the same.

The present invention relates to a process for the production of crystal-clear (transparent) polyamide.

Polyamides or copolyamides, which using dicycan type amines, i.e. Di- (4-aminocyclohexyl) alkane compounds and 4,4'-diamino-dicyclohexyl, have been known for a long time. However, all copolyamides obtained to date have disadvantages, be it in terms of their processability, be it in terms of their mechanical properties, be it in terms of the stability of transparency in boiling water or organic liquids or solutions, or be it in terms of the price of the raw materials to be processed. Liquid isomer mixtures of these amines are generally used.

The class of dicycan type amines has already been described in British Pat. No. 619,707. Although the copolyamides obtainable from the diamines mentioned in this patent already have good properties, a further improvement in their processability and further properties, such as the transparency resistance to boiling water and the resistance to solvents and solvents as well as the hydrolysis degradation is desirable and provides this

The aim of this invention is also interested in formulations which allow the use of cheaper raw materials.

This and the other known processes for the preparation of transparent copolyamides using diamines of the dicycan type (CH-PS 449 257, US Pat. No. 2,494,563, 3,842,045.3 840 501 Japn. Ann. 7 211 502) In addition to the dicycandiamine, mainly use long-chain, relatively expensive dicarboxylic acids, such as azelaic acid, sebacin-lo acid, dodecanedioic acid, in order to arrive at products which have a not too high melt viscosity which is tolerable for processability, e.g. B. below 10,000-20,000 poise at 300 ° C.

If you use only the relatively cheap adipic acid as the acid component, you often get discolored end products whose glass transition temperature and melt viscosity is so high at usual processing temperatures that to reduce these temperatures co-components such. B. so-called AH salt (adipic acid hexa-20 methylenediamine salt), or caprolactam must be added. The polyamides produced in this way are poorly resistant to hot water and solvents and have a relatively high water absorption capacity, which is associated with changes in volume of the injection molding which occur in the course of conditioning during the injection molding process.

US Pat. No. 2,696,482 describes a transparent polyamide made from dicycan and isophthalic acid, which is well resistant to hot water. For an advantageous course of the condensation reaction, however, the diphenyl ester of isophthalic acid must be used as the starting point, or phenol must be added to the polycondensation mixture as a solvent or plasticizer. Because of the high softening temperature and the high melt viscosity of the resulting polyamide melts, processing temperatures of around 330 ° C are required. The maximum 35 times water absorption of this product is 7.75%.

The copolyamides from an isophthalic-terephthalic acid mixture mentioned in US Pat. No. 3,847,877, which also additionally contain nylon 6 as co-component, show a similarly high water absorption capacity and tend to be completely softened and clouded after 40 boiling water treatments .

The transparent polyamides mentioned in US Pat. No. 3,597,400, which are produced from an isophthalic acid-terephthalic acid mixture and a dicycan-diaminohexane mixture with a large proportion of diaminohexane as the diamine component, have a water absorption capacity which is much too great. When such polyamides are stored in water, the softening point is lowered to 50-60 ° C.

Surprisingly, it has now been shown that it is possible to produce transparent, transparent polyamides with good mechanical properties and excellent resistance to transparency in chemical water if the process is carried out in accordance with the patent claim.

The polyamide-forming function means either the lactam-55 configuration or the group pair NH2 / —COOH.

If compounds according to c2) are used as component c), that is to say salts or mixtures of equimolar amounts of an aliphatic dicarboxylic acid and a diprimary aliphatic diamine, then both the diamine and the 60 dicarboxylic acid must contain at least 6 methylene groups and these must each be selected such that in c) an average of at least 9 methylene groups are present between the NH2 and COOH groups (or in the end product between the NHCO groups).

65 The diamines according to a) are primarily bis (4-amino-3-methyl-cyclohexyl) methane and 2,2-bis (4-amino-cyclohexyl) propane. But also with the (4,4'-diamino-dicyclohexyl) methane and the 1,2-bis- (4-

3rd

624 970

amino-bicyclohexyl) -ethane can be used to produce valuable products. In practice, isomer mixtures of such a diamino compound which are liquid at 25 ° C. are preferably used.

The components according to b) are preferably isophthalic acid alone or a commercially available mixture of isophthalic acid and terephthalic acid (e.g. 95: 5, molar).

If up to 15 mol% of isophthalic acid or of the isophthalic acid-reterephthalic acid mixture have been replaced by other polyamide-forming dicarboxylic acids, such co-acids are advantageously aliphatic dicarboxylic acids, specifically suberic acid, azelaic acid, sebacic acid and dodecanedioic acid.

The following are particularly suitable as component c): ci) (O-aminolauric acid or preferably its lactam, or a> -amino-undecanoic acid, or c2) salts and mixtures of the equimolar amounts of the following diamines and dicarboxylic acids, in particular of a, co- Diaminoalkanes and a, oo-alkanedicarboxylic acids.

Diamines: 1,6-diaminohexane, 1,8-diaminooctane, 1,9-diamino-nonane, 1,10-diamino-decane, 1,12-diaminododecane. Dicarboxylic acids: azelaic, sebacic, or dodecanedioic acid.

If c) represents a lactam or a to-amino acid according to ci), its equivalent weight (for its reaction with the other reaction partners) is identical to the molecular weight. For salts or mixtures of diamine and dicarboxylic acid according to c2), the equivalent weight is half the sum of the molecular weight of the diacarboxylic acid and the diamine.

The condensation of the reaction mixture from a), b) and c) is advantageously carried out in the melt and according to the known polycondensation methods. The diamine and the dicarboxylic acid must be present in equivalent amounts so that products with the required molecular weights can be obtained. The chain length of the product can be regulated with deliberately used excesses of diamine or of diacarboxylic acid in the reaction mixture. The chain length can also be limited by adding a calculated amount of monoamine or monocarboxylic acid to the reaction mixture.

Component a) and b) can also be used in the form of their salts.

Before, during or towards the end of the polycondensation, the additives which are customary in the production of polyamides and which are advantageously soluble in polyamide can be added to the polycondensation mixture. These are, for example, light and heat stabilizers (e.g. aromatic amines, such as diphenylamine, phosphorus compounds, such as phosphorous acid, as well as soluble metal complexes, e.g. of copper or manganese), dyes, optical brighteners, plasticizers, mold release agents, or flame retardants. In the event that the transparency of the polyamides plays a less important role than their mechanical properties, reinforcing materials such as glass fibers or asbestos fibers, glass beads or mineral fillers can also be added to the end products. Many of these additives can of course also be rolled on and extruded into the polymer mass.

The end products obtained according to the invention are temperature-resistant, and the mixtures hardly tend to discolor during polycondensation, even at temperatures of 280-320 ° C. Furthermore, they have glass transition temperatures of approximately 140-170 ° C, in particular 150-170 ° C and show a stability of the transparency in boiling water of several weeks.

The melt viscosity of the end products obtained according to the invention at 300 ° C. with average polymer degrees of polymerisation of 80-200, whereby each building block is regarded as a chain link, is approximately 1500-15,000 poise, in particular approximately 4000 to 10,000 poise. This ensures flawless workability on injection molding machines.

The copolyamides obtained according to the invention are well suited for use in the so-called injection molding process for producing a wide variety of molded parts. Depending on the melt viscosity of the granulate used, melt temperatures of 270-310 ° C or higher temperatures are possible, with the risk of discoloration being low. The material shows good flow and demolding properties. In order to achieve a better mold filling, the shaped structures, e.g. Tools that are tempered without affecting the mold release. It is generally not necessary to powder the granules with lubricants such as calcium or magnesium stearate.

The transparent polyamides according to the invention can also be used to produce blends with other homopolyamides or copolyamides or mixtures thereof, which e.g. can be done by mixing the granules of the polyamides and then performing an extrusion. Additional homopolyamides include Nylon 12, Nylon 6 or Nylon 66, as copolyamides e.g. those which contain the monomers which lead to the homopolyamides mentioned, into question. These further polyamides are preferably added in an amount of 0-50% by weight, based on the resulting alloy. By adding a further, polyamide-compatible polymer to the polyamide according to the invention, the mechanical properties of the original polyamide can also be changed, e.g. the impact or notched impact strength can be improved.

If a polyamide is used in so-called alloying, e.g. Nylon 12, the transparency resistance of the alloy in boiling water is only slightly influenced.

The following examples illustrate the invention.

Where:

IPS-95: isophthalic acid, containing 5 mol% terephthalic acid

(AMOCO, Chem. Corp., Chicago, USA)

Knockout time: the total condensation time in hours Ko. temp .: the maximum condensation temperature in the

Final phase of the polycondensation.

T) Rei. : the relative solution viscosity, measured on a 0.5% solution of the polymer in meta-cresol. DTA, TG: the glass transition temperature, measured on a dried sample of the end product, using a differential calorimeter, type 1B, from Perkin-Elmer, at a heating rate of 32 ° C./min. and a sensitivity according to R 16.

T] enamel: the enamel viscosity; this is a measure of the flow behavior of the polyamide melt and was carried out at a melt temperature of 290 ° C and a load of 12.5 kp with a melt index device from Goettfert type MFI 21.6 using a nozzle 8 mm long and 2.1 mm in diameter , certainly.

Transparency resistance in boiling water:

very good: a plate has a transparency resistance in boiling water of several weeks. good: a plate has a transparency resistance in boiling water of about 3 days. medium: a plate has a transparency resistance in boiling water of about 1 day.

bad: a plate becomes cloudy in boiling water within a few hours.

s io

15

20th

25th

30th

35

40

45

50

55

60

65

624 970 4

In table 1) the first main column contains the type and parts by weight of component c). The second main column contains the equivalent ratio of the starting materials used a), b) and c), whereby for the purpose of a direct comparison, with component c), in part s amino acids and partly salts (according to d or c2 according to Claim) are used, the formula unit relates to a pair of polyamide-forming groups.

Examples 1-4 io

In the examples summarized in the following table, component c) was varied.

4,4'-Dia-mino-3,3'-dimethyI-dicyclohexyImethane in the form of the commercially available, liquid isomer mixture, data sheet D 075 (1970) from BASF, Ludwigshafen, FRG, and as component b ) IPS-95 used, the molar ratio of amine to IPS-95 was 1: 1. The weight fraction of the added component c) in the above examples was between 36 and 39%, based on the sum of the starting materials a) + b) + c); the equivalent proportion of component c) varies between 1.1 and 1.55 parts per mole of component b). The amount of component c) was determined as follows: per pair of amide bonds, originating from components a) (amine as defined) and b) (IPS-95), 12 2s carbon atoms are to be introduced through component c) into the polyamide chain of the end product.

This gives the following formula: The equivalent part to be determined aM of c) multiplied by the mean number of C atoms Nc of c) gives the constant value of 13, or expressed algebraically as:

aMNc = 13 or aM =

The evaluation of this relationship in the above examples shows that the amount of component c) added which is advantageously required is 35-40% by weight, based on the sum of the starting materials a) + b) + c). The additives with the larger, average number of methylene groups are preferred, e.g. the aminolauric acid (or laurolactam) and the salt from diaminododecane with sebacic or dodecanedioic acid.

In addition to good processability, all of the end products obtained according to these examples are distinguished by very good stability of the transparency in boiling water.

Example 5 (comparative example)

The proportions of component c) are in a range where fully transparent polyamides are still obtained, but the transparency resistance in boiling water no longer reaches the values of the products listed in Examples 1-4. The material remains transparent in boiling water for only a few hours.

Working procedure Examples 1-5

The components were weighed into a condensation apparatus made of glass, the air was completely replaced by nitrogen, the apparatus was immersed in a molten salt, and the temperature was raised to approximately 230 ° C. while stirring the starting material mixture. The precondensation started and the bulk of the water of reaction distilled off. The melt became increasingly viscous. Therefore, the temperature was raised gradually, reaching a value of 280-300 ° C after about 1 hour. The experiment was ended after a total condensation time of 3.5-6 hours. The stirrer was removed from the melt and, after solidification, knocked out of the glass tube. The analytical values listed in the table were determined on the completely transparent materials.

Table 1

Bs

Component c)

Ratio equivalent

Condensation conditions

Analyzes

No.

Art.

Gew.-Cf a)

b)

c)

Knockout time dead. (h)

Knockout temp. Max. (° C)

T] rei. 0.5% m-kr

DTA

TG, ° C

> 1 enamel (poise) 12.5 kp,

290 ° C

Transp. Best, in boiling water

1

Aminolauric acid

36.5

1

1

1.1

3.8

280

1.46

156

2,700

very well

2nd

Aminoundecanoic acid

37

1

1

1.2

3.5

280

1.46

157

4,000

Good

3rd

12.12 salt

36.5

1

1

1.1

4.0

280

1.53

153

6,000

Good

4th

12.10 salt

37

1

1

1.2

5.5

280

1.59

170

12,000

Good

5

Aminolauric acid

44.0

1

1

1,485

6.0

280

1.52

138

2,600

bad

Examples 6-8

The composition of the starting materials is shown in Table 2.

In this table:

Dimecycan: the 4,4'-diamino-3,3'-dimethyldicyclo-hexylmethane

Dicypropane: the 2,2-di (4-aminocyclohexyl) propane dicycan: the (4,4'-diaminodicyclohexyl) methane.

Column 1 in Table 2 gives the molar proportions of the individual diamines, based on the sum of all diamines according to a).

65

In all three examples, beautifully transparent products were obtained, which are good for an application, e.g. suitable for injection molding. For more information, see table 2.

5

Table 2

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Vs amine according to a)

Art.

Equivalent ratio of condensation conditions analyzes

Mol-amine IPS add. c Ko. time Ko. temp. t] rei. Share dead. ALS tot. (H) max. (° C) 0.5%

% m — Kr

DTA T | Enamel transp.

TG, ° C (poise)

12.5 kp, the water 290 ° C

'50 150

g f Dimecycan f 5

\ Dicycan \ 5

j f Dimecycan / 50

\ Dicypropane \ 50

Dicycan

100

1 1.1 3.5 280 1.622 147 10,000 good

1 1.1 5.0 300 1.677 151 24 000 good 1 1.1 6.3 280 1.633 143 7 000 massive

15

Example 9

In a polycondensation autoclave, 11.50 kg of the liquid isomer mixture of (4.4'-diamino-3.3 / -dimethyldicyclohexyl) methane and 10.50 kg of laurolactam were stirred with 20 3 kg of water with slow heating to 180 ° C. Now, with stirring, 8.00 kg of isophthalic acid of the type IPS-95 were sprinkled into the melt within a quarter of an hour, so that a homogeneous suspension was formed, to which 29 g of benzoic acid and 3 g of an anti-foaming agent based on 2 s silicone were added. The autoclave was now sealed gas-tight, with the resulting melt being under a cushion of water vapor. With further stirring, the melt was heated to 280 ° C. A pressure of 20 atu built up, which was now maintained for 30 hours. The pressure was then slowly reduced again to atmospheric pressure and the melt was then condensed at 280 ° C. for 2 hours under a stream of nitrogen. Finally, the melting temperature was raised to about 300 ° C. and stirring continued for about 4 hours until the melt no longer showed an increase in viscosity.

The product was then discharged from the autoclave and granulated. Its relative solution viscosity is 1,512 and its melt viscosity at 280 ° C is 10 500 poise, measured <»0

at a load of 12.50 kg. Its glass transition point is 151 ° C.

ASTM tension rods and small DIN beams were sprayed on an injection molding machine at a cylinder temperature of 280 ° C, and the mechanical properties were tested on them.

The flow resistance and breaking strength according to DIN 53455 were 950 and 650 yes kp / cm. The limit bending stress according to DIN 53452 was determined to be 1200 kp / cm. When determining the impact strength according to DIN 53453, no breakage of the material occurred. The material's impact strength according to DIN 53453 is 2 cm kp / cm. The material has a ball pressure hardness according to VDE 0302 after 60 seconds of 1100 kp / cm2.

Its equilibrium water absorption is 23 ° C and 50% pure. Air humidity at 1.4% and after water storage (boiling) at 3.4%.

With the transparent polyamides on the market, the moisture absorption is significantly higher under the conditions mentioned.

As a result of the comparatively very low moisture absorption, the mechanical properties of the material change only slightly in water. In addition, the dimensional stability of injection molded articles made from the polyamide according to the invention is very good.

B