WO1994017124A1

WO1994017124A1 - Process for the preparation of a nylon block copolymer

Info

Publication number: WO1994017124A1
Application number: PCT/NL1994/000015
Authority: WO
Inventors: Wilhelmus Gerardus Marie Bruls; Henricus Joseph Marie Van Der Loo; Albert Arnold Van Geenen
Original assignee: Dsm N.V.
Priority date: 1993-01-27
Filing date: 1994-01-24
Publication date: 1994-08-04
Also published as: BE1006638A3; AU5950394A

Abstract

Process for the preparation of a nylon block copolymer in which two or more reaction streams are combined, which reaction streams contain one or more polyols and/or polyamines, lactam-blocked polyisocyanates and catalysts, which may be dissolved in lactam or not, the catalysts and lactam-blocked polyisocyanates being present in different streams, in which the flows, whether or not pre-mixed, are metered to an extrusion device having a feed zone temperature of 80-180 °C and a cylinder temperature of 185-300 °C. The advantage is that the reaction rate increases in comparison with the RIM process, but also that nylon block copolymers with improved impact strength are obtained while the elastomer content remains unchanged.

Description

- 1 -

PROCESS FOR THE PREPARATION OF A NYLON BLOCK COPOLYMER

The invention relates to a process for preparing a nylon block copolymer in which two or more reaction streams are combined, which reaction streams contains one or more polyols, lactam-blocked poly-isocyanates and catalysts, which may be dissolved in lactam or not, the catalysts and lactam-blocked poly-isocyanates being present in different streams. Such a process is described, inter alia, in EP-A-0320070, where a nylon block copolymer is obtained by combining two or more reaction streams, each having a temperature of 68-95°C, in a mold having a temperature of 100-180°C. A prepolymer is formed at about 68-95°C by the reaction between at least one polyol and lactam-blocked poly-isocyanate. The nylon block copolymer is thereafter formed at a temperature of 100-180°C. In this process a nylon block copolymer is obtained in which the polyol is distributed homogeneously over the nylon matrix, resulting in excellent impact strength. The disadvantage, however, is that the reaction rate is low so that an article can be prepared only once every 4-10 minutes, this depending on the weight and wall thickness of the article.

The object of the invention is to provide a simple process that does not have the above-mentioned disadvantage. To achieve this, the two or more reaction streams are metered to an extrusion device with a feed zone temperature of 80-180°C and a cylinder temperature of 185-300°C, preferably between 190-280°C. The two or more streams can be metered direct to the extrusion device, but they may also be mixed shortly beforehand and be metered immediately after mixing. At a low reaction temperature then first the reaction product of a polyol and/or polyamine with the lactam-blocked polyisocyanate is formed, following which the nylon block copolymer is formed at higher reaction temperature. Subsequently, this nylon block copolymer can be obtained in, for example, granulate form. This granulate can be processed into articles by means of the customary processing techniques, such as injection moulding. It is also possible to start from a stream that already contains the reaction product of a polyol and/or polyamine with the lactam-blocked poly- isocyanate and a second flow containing the catalyst. This has the advantage that an article can be prepared every 20 seconds to 3 minutes, depending on the weight and wall thickness of the article. Surprisingly, it was also found that a higher impact strength was obtained with the same elastomer content.

Nylons, or polyamides, are known polycondensates of for example aliphatic dicarboxylic acids containing 4- 12 carbon atoms with aliphatic diamines containing 4-12 carbon atoms and/or lactams containing 4-12 carbon atoms. Examples of polyamides are: polyhexamethylene adipamide (nylon 6,6), polyhexa- methylene azelamide (nylon 6,9), polyhexamethylene sebacamide (nylon 6,10), polyhexamethylene lauramide (nylon 6,12), polytetramethylene adipamide (nylon 4,6), polycaprolactam (nylon 6) and polylaurinolactam (nylon 12). The diamines and/or dicarboxylic acids can also be aromatic.

Polyamides can also be built up of two or more dicarboxylic acids and/or two or more diamines, or of two or more lactams, while they can also consist of mixtures of two or more polyamides.

Polyamides have numerous applications. For certain of these, it is often desirable to modify the properties of polyamides. Modification of properties is usually effected by synthesizing block copolymers which consist of one or more polyamide blocks and one or more blocks of another polymer. It is, for example, known that hydrophobic blocks in, for example, polycaprolactam, can make the polycaprolactam less hydrophilic, which hydrophilic character is sometimes undesirable. And polylactampolyether block copolymers, for example, possess a combination of properties rendering them very suitable for use in so-called engineering plastics.

The polylactam-polyether block copolymers, can be prepared by reacting a polyol or a polyether amine with an activator and converting the resulting prepolymer into a nylon block copolymer under the influence of a catalyst. As activator use can be made of a lactam-blocked pol isocyanate.

With the term 'lactam-blocked polyisocyanates' is understood the reaction product of a polyisocyanate with a lactam, more in particular caprolactam. In principle it is assumed that almost all isocyanate groups have reacted with a lactam molecule, yielding the following compound:

H 0

I II R ( - N - C - ( - L))_n

where - (- L) represents an unopened lactam ring, R a cyclic or non-cyclic alkyl, aralkyl, alkaryl or aryl group, and n an integer greater than or equal to 2. In general, polyisocyanates having at least two isocyanate groups and 4-25 carbon atoms can be applied. Preferably, aliphatic diisocyanates are used and include, for instance 1,4-butane diisocyanate, 1,5-hexane diisocyanate and 1,6-hexane diisocyanate. Araliphatic, cycloaliphatic and aromatic isocyanates can also be used and include, for instance isophorone diisocyanate, 2,4- and 2,6-toluene diisocyanate, 2,2-, 2,4- and 4,4-diphenyl methane diisocyanate (MDI) and polyphenylene - polymethylene polyisocyanates. The reaction product of a polyol and a lactam- blocked polyisocyanate is known, and an exemplary process is described in EP-A-0135,233. The product prepared by that process is an N-substituted carbamoyl lactam compound. To prepare this compound, a polyol and a lactam- blocked polyisocyanate in molten condition are reacted in the presence of a suitable catalyst, preferably a Lewis acid. The reaction is preferably carried out in molten lactam, and most preferably in molten caprolactam. Compounds of for instance the following formula are formed:

0 H H 0

R - [A- (-L-)_yi - C - N - R¹ - N - C - (~L)]_xi

wherein:

A represents 0 or NH R represents a polyether or hydrocarbon residue derived from a polyol of the formula R-(0H)_xi or a polyamine of the formula R-(NH₂)_xi xi represents an integer > 2

R¹ represents an alkyl, aralkyl or alkaryl group, whether or not cyclic yi represents an integer > 0

(-L) represents an unopened lactam ring

(-L-) represents an opened lactam block

In the process according to the present invention, polyols according to the following general formula are used:

R-(-OH)x

where x is an integer greater than or equal to 2, and preferably 2 to 4.

The R group in the formula R-(-OH)x can represent a hydrocarbon group (preferably having a molecular weight of at least 100), a polyether group, a polyester group or a polysiloxane group.

The molecular weights of polymers or polymer segments given herein refers to the number average molecular weight, which may be determined by known techniques such as gel-phase chromatography.

Polysiloxane groups or polysiloxane segments include groups or segments containing at least 50 per cent by weight of one or more units of the following formula:

A -(-Si-O-)- A

where A represents methyl or phenyl.

Polysiloxane groups or segments usually contain other groups, such as for example ether groups with lower alkyls such as ethane or methane. Such ether groups are often terminal groups in the chain of repeating siloxane units. These ether groups can account for up to 50 per cent by weight of the polysiloxane group. By preference they account for less than 30 per cent by weight.

Preferably, however, R is a hydrocarbon group, a polyether group or a polyester group. Examples of hydro¬ carbon groups are alkylene groups. In the case of diols hydrocarbon groups include alkylene groups such as ethylene glycol or polymeric hydrocarbons such as segments of polybutadiene containing two or more hydroxyl groups. A polyoxypropylene segment containing two or more hydroxyl groups is an example of a polyether group.

Examples of compounds which contain hydroxyl groups and which can be applied in the above-mentioned process are diols, triols and tetraols such as ethylene glycol, propylene glycol, poly(oxybutylene) glycol, poly(oxyethylene) glycol, poly(oxypropylene)diol, pol (oxypropylene)triol, pol (oxypropylene)tetrol, polybutadiene diol, polydimethyl siloxanes containing hydroxyl groups and combinations of these, for example block copolymers of poly(oxypropylene) and poly(oxy- ethylene) containing hydroxyl groups. However a polyol obtained by ethoxylation and/or propoxylation of, for example, ethylene amine, glucose, fructose, saccharose and the like can also be used. Use can also be made of polyester polyols such as caprolactone diol.

The polyols described herein are mainly polymeric polyols. The weight average molecular weight of these polyols is at least 500, and generally ranges between 1000 and 10,000, although molecular weights of between 2000 and 8000 are preferred. The polyol provides an elastomer segment in the nylon block copolymer to be prepared while the hard crystalline segment in the nylon block copolymer is provided by the lactam polymerization. Elastomer segments contribute to a glass transition temperature Tg below 0°C, preferably below -25°C, once they are incorporated in the nylon block copolymer. The glass transition temperature is determinable using

Differential Scanning Calorimetry under nitrogen at a scan speed of 10-20°C per minute.

In place of polyols, use can also be made of polyamines or mixtures of polyols and polyamines in the subject invention, The polyamines used are polyamines with at least two primary amine groups and are preferably selected from the group consisting of polyoxyalkylene poly-amines, polyalkadiene polyamines, polyalkene polyamines and combinations of these. The polyamines have an average molecular weight of about 300 to about 10000, preferably at least 500, while an average molecular weight of at least 1000 is prefered. This molecular weight being chosen so that the poly-amine provides the polyamide ultimately prepared with an elastomer segment, while the hard crystalline segment in the polyamide is provided by the lactam polymerization.

Elastomer segments contribute to a glass transition temperature Tg of below 0°C, preferably below - 25°C, once they are incorporated in the nylon block copolymer.

The amount of elastomer segments in the nylon block copolymer can vary between 1 and 90 per cents by weight, depending on the properties desired. Preferably, use is made of between 5 and 70 per cents by weight of elastomer, more particularly between 10 and 60 per cents by weight. Suitable polymeric hydrocarbon polyamines include, among others, polybutadiene diamine, polybutadiene polyamines and butadiene-acrylonitrile polyamines. Examples of suitable polyether polyamines are pol (oxybutylene)diamine, poly(oxyethylene)diamine, poly(oxypropylene)diamine, poly(oxypropylene)triamine, poly(oxypropylene)tetramine and combinations thereof such as, for example, block copolymers of pol (oxypropylene) and pol (oxyethylene) with at least two functional amine groups. Polyether polyamines preferably applied are poly(oxypropylene)triamines with an average molecular weight of at least 2000.

The process is carried out with alkali lactamate such as sodium lactamate and/or potassium lactamate and/or a Lewis acid as catalyst. Examples of suitable Lewis acids are bromomagnesium lactamate, magnesium bislactamate, magnesium acetyl acetonate, magnesium salts of organic carboxylic acids such as magnesium stearate, magnesium chloride, calcium ethoxide, calcium lactamate, calcium acetyl acetonate, barium lactamate, barium chloride, barium acetyl acetonate, zinc chloride, zinc acetyl acetonate, zinc lactamate, cadmium chloride, cadmium acetyl acetonate, cadmium lactamate, boron acetyl acetonate, aluminium trilactamate, aluminium chloride, chloroaluminium dilactamate, lactam aluminium chloride, tin II chloride, tin II ethoxide, tin II acetyl acetonate, titanium trichloride, titanium (III) acetyl acetonate, titanium (III) ethoxide, vanadium (III) ethoxide, vanadium (III) acetyl acetonate, vanadium (III) chloride, chromium (III) chloride, chromium (III) acetyl acetonate, iron (III) chloride, iron (II) acetyl acetonate, ferrous acetyl acetonate, cobalt (II) chloride, cobalt (II) acetyl acetonate, nickel acetyl acetonate, nickel chloride, chromium (III) acetate, copper (II) acetyl acetonate. Preferably, as Lewis acid use is made of magnesium bislactamates such as caprolactamate and/or pyrrolidonate.

Lactams useful in the present proces are molten lactam, preferably molten caprolactam, but this process can also be carried out with other lactams, such as laurinolactam. In the preparation of the nylon block copolymer it may be essential to carry out the polymerization in the presence of one or more compounds normally applied in nylon block copolymers, such as fillers, plasticizers, flame retardants, stabilizers and reinforcing materials such as mica or glass fibres.

The invention will be further explained by the following non-limiting examples.

Example I

Feed hopper (A) of a twin-screw extruder was fed with a mixture of 104 kg of caprolactam-blocked 1,6-hexane diisocyanate and 356 kg of caprolactam.

Catalyst vessel (B) was fed with a mixture of 136 kg of potassium caprolactamate solution (1 molar in caprolactam) and 700 kg of caprolactam.

Elastomer vessel (C) was fed with 376 kg of Caradol^R36-3 (triol from Shell, molecular weight 4700). From the three vessels flows A, B and C were passed to the feed zone of a ZSK-40 (twin-screw extruder from W&P) in the ratio A:B:C = 1:2:0.9. The temperature setting of the extruder was 220-275°C and the screw speed 150 rpm. The average residence time in the extruder was 2 minutes and 55 seconds. In the last extruder zone water was injected to eliminate the catalyst activity and the non-converted caprolactam (approx. 10%) was removed by means of a vacuum. Test bars were prepared from the dried granulate, and of these bars the notched impact strength (Izod according to ASTM D256) and the E-modulus (according to ASTM D790) were determined. Izod : 54 kJ/m² E-modulus : 1460 N/mm² Exampl e I I

Example I was repeated, flows A, B and C first being mixed by means of a static mixer and metered to the twin-screw extruder immediately after mixing. Of the granulate obtained the Izod value and the E-modulus were determined. Izod : 53 kJ/m² E-modulus : 1420 N/mm²

Example III

In a feed hopper (A) of a ZSK-40 twin-screw extruder 105 kg caprolactam-blocked 1,6-hexanediisocyanate and 217 kg caprolactam were mixed.

In catalyst vessel (B) 109 kg potassium caprolactamate (1 molar in caprolactam) and 560 kg caprolactam were mixed.

Elastomer vessel (c) was fed with 380 kg Caradol® 36-3.

From the three vessels streams A, B and C were passed to the feed zone of a ZSK-40 in the ratio A:B:C = 1:2:1.3.

The temperature setting of the extruder was 220-275°C and the screw speed 150 rpm. The average residence time in the extruder was 2 minutes and 40 seconds. The product obtained was cooled down to 150°C under nitrogen and granulated. The granulate was kept at 150°C during 30 minutes to reduce the residence monomer content. The resulting nylon block copolymer had an IZOD value of

50 KJ/m², an E-modulus of 150 N/mm² and a water soluble extract of 1,8 weight process.

Comparative example A In a feed hopper (A) of a RIM nylon machine 225 g of Caradol^R36-3, 72 g of caprolactam-blocked 1,6-hexane diisocyanate and 203 g of caprolactam were mixed and heated at 80°C.

In catalyst vessel (B) a solution of 81.2 g of potassium caprolactamate (1 molar in caprolactam) and

418.8 g of caprolactam were also heated to 80°C. Subsequently, 200 g of a 1:1 mixture of A and B was transferred to a steel plate mould (3.2 mm) heated at 140°C.

The resulting nylon block copolymer in dry condition had an Izod value of 47 kJ/m² and an E-modulus of 1420 N/mm².

Claims

C A I M S

1. Process for the preparation of a nylon block copolymer in which two are more reaction streams are combined, which reaction streams contain one or more polyols and/or polyamines, lactam-blocked poly¬ isocyanates and catalyst, which may be dissolved in lactam or not, the catalysts and lactam-blocked polyisocyanates being present in different streams, this process being characterized in that the flows are metered to an extrusion device with a feed zone temperature of 80-180°C and a cylinder temperature of 185-300°C.

2. Process according to claim 1, characterized in that the streams are combined in an extrusion device having a cylinder temperature of 190-280°C.

3. Process according to either claim 1 or claim 2, characterized in that as lactam-blocked poly- isocyanate use is made of an aliphatic di- or polyisocyanate.

4. Process for the preparation of nylon block copolymers as substantially described in the description and the examples.

5. Articles prepared from a nylon block copolymer obtained according to the process of one of the preceding claims.