NO309485B1 - Flexible translucent mixture, as well as its use - Google Patents

Abstract

A translucent, flexible compsn. contains: (A) 50-95 wt.% of (1) a polyamide resin (PA) with light transmission at 700 nm above 15% (above 30%) (1 mm plate), (2) additives, e.g. stabilisers, demoulding agents, lubricants, crystallisation accelerators, pigments, dyes, organic and/or mineral fillers, and antioxidants, and (3) 0-50% (less than 20%), w.r.t. (A), of a plasticiser; and (B) 50-5% (10-40%) of (a) a terpolymer of ethylene, an alkyl (meth)acrylate and an anhydride of an unsatd. dicarboxylic acid, and (b) an ethylene/alkyl (meth)acrylate copolymer, in ratio of (b)/(a) or 1/30-2 (not above 2/3). The modulus of flexing (ISO 178) of the compsn. is <2/3 (<1/3) of the modulus of flexing of PA and below <750 MPa (<500 MPa).

Description

The present invention relates to a flexible, translucent mixture as stated in claim 1's preamble, as well as application as stated in claim 5.

Mixtures with a matrix containing polyamide and ethylene polymers are previously known for their impact strength.

In particular, EP 096,264 describes a material with high impact strength and which contains: (A) a thermoplastic polyamide with a relative viscosity of 2.5-5, and (B) 5-60% by weight in relation to (A) of a non -cross-linked terpolymer consisting of:

(a) 55-79.5% by weight ethylene,

(b) 20-40% by weight of at least one primary or secondary alkyl (meth)acrylate, and (c) 0.5-8% by weight of a functional acidic monomer, (for example maleic anhydride). EP 218,665 describes mixtures containing 50-95% by weight of at least one polyamide resin and 5-50% by weight of at least one ethylene polymer containing 0.9-16 mol% units derived from maleic anhydride and/or from at least one alkyl acrylate or methacrylate in which the alkyl group contains 1-6 carbon atoms . This ethylene polymer is present in the form of a mixture of ethylene-alkyl (meth)acrylate copolymers (A) and of ethylene-maleic anhydride-alkyl (meth)acrylate polymer (B), the (A)/(B) weight ratio being in the range 1/ 3-3.

EP-A-072,480 describes an impact-resistant composition comprising 50-90% by weight of polyamide, 1-45% by weight of an ionomeric ethylene resin and 0.5-40% by weight of an elastomeric ethylene copolymer.

Finally, US patent no. 3,373,223 describes a polymer alloy mainly consisting of 25-90% by weight polyolefin, 5-70% by weight polyamide and 1-10% by weight of an ethylene

(meth)acrylic acid copolymer.

However, these compounds, which have an improved impact strength compared to the polyamide matrices used alone, require higher processing temperatures, often exceeding 270°C - and they are generally not both translucent and flexible.

A translucent mixture based on a polyamide resin, which is very flexible and easy to process, especially by extrusion, has now been found, which mixture is characterized by the fact that it includes:

(A) 50-95% by weight

1) at least one polyamide resin (I) whose light transmission at 700 nm is greater than 15% and preferably greater than 30% (through a sheet with a thickness of 1 mm), 2) various additives (IV) such as stabilizers, mold release agents, lubricants, crystallization accelerators, pigments, organic and/or inorganic fillers or colors, or antioxidants, 3) possibly at least one softening agent (V) which constitutes 0-50% by weight of (A) and preferably less than

20% by weight of (A),

(B) 5-50% by weight and preferably 10-40% by weight:

(a) at least one ethylene alkyl (meth)acrylate unsaturated i

carboxylic acid anhydride terpolymer (II),

(b) at least one ethylene-alkyl (meth)acrylate copolymer

(III)

where 1/30 s (b)/(a) s 2 and preferably (b)/(a) s 2/3

and such that its flexural modulus, determined according to ISO standard 178 is less than or equal to 2/3 of the flexural modulus of the PA resin (I) alone and is certainly less than 750 MPa and preferably less than or equal to 1/3 of the flexural modulus of the PA resin ( I) alone and absolutely less than 500 MPa.

The mixture is characterized by what is stated in the characterizing part of claim 1.

Preferably, the terpolymer (II) comprises 11-99.2 mol% of at least one unit derived from ethylene, 0-20 mol% of at least one unit derived from alkyl (meth)acrylate(s) and 0.8-3 mol% of at least one unit derived from unsaturated dicarboxylic acid anhydride(s), preferably of at least one maleic anhydride derivative, and has a melting index in the range 0.1-400 g/10 min., determined according to NFT standard 51-016 (190°C, load 2.16 kg) . For the sake of simplicity, the term "terpolymer" will be used in the following text, even in those cases where (II) does not contain any unit derived from alkyl (meth)acrylate(s).

Preferably, the copolymer (III) comprises at least 78 mol%

units derived from ethylene and up to 22 mol% of at least one unit derived from alkyl (meth)acrylate(s) and has a melt index in the range 0.1-400 g/10 min., determined according to NFT standard 51-016 (190 °C, load 2.16 kg).

The alkyl groups in the alkyl acrylate or methacrylate present in the terpolymers (II) and/or the copolymers (III) can be linear, branched or cyclic and aliphatic, cycloaliphatic and/or aromatic and can contain up to 10 carbon atoms.

As examples of alkyl in acrylate or methacrylate from which the terpolymers (II) and/or copolymers (III) are derived, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate can be mentioned in particular. Of these, alkyl acrylates and methacrylates, ethyl acrylate (EA), n-butyl acrylate (BA) and methyl acrylate (MA) are particularly preferred.

As examples of unsaturated dicarboxylic anhydrides from which the terpolymers (II) are derived can be mentioned itaconic anhydride, citraconic anhydride, 2-methylmaleic anhydride, 2,3-dimethylmaleic anhydride, bicyclo[2.2.2]oct-5-ene-2,3- dicarboxylic anhydride and, in particular, maleic anhydride.

Polyamide resin according to the invention is understood to mean polyamides or PAs which contain aliphatic units containing at least 7 carbon atoms and/or cycloaliphatic units and/or aromatic units.

Mention may be made, for example, of resins obtained by polycondensation of one or a number of lactams or of a, w-amino acids or by substantially stoichiometric polycondensation of a number of one or more aliphatic diamines and of a number of aliphatic dicarboxylic acids. It is also possible to use an excess of diamine, so that an excess of amine end groups is obtained in relation to the carboxyl end groups in the polyamide.

The lactams contain at least 7 carbon atoms and preferably at least 10 carbon atoms. The preferred lactams are decalactam, undecalactam and dodecalactam.

The preferred α,β-amino acids are 10-aminodecanoic acid, 11-aminoundecanoic acid and 12-aminododecanoic acid.

The aliphatic diamines are a,co-diamines containing, between the end amino groups, at least 6 carbon atoms and preferably 6-10 carbon atoms. The carbon chain can be linear (polymethylenediamine) or branched. Preferred diamines are hexamethylenediamine (HMDA) and dodecamethylenediamine.

The aliphatic dicarboxylic acids are α,α>-dicarboxylic acids with at least 5 carbon atoms (not including the carbon atoms in the carboxyl groups), and preferably at least 6 carbon atoms, in a linear or branched carbon chain. Preferred diacids are azelaic acid, sebacic acid and 1,12-dodecanoic acid.

As examples of such PA resins can be mentioned: polyhexamethylene sebacamide (PA-6,10), polyhexamethylene dodecaneamide (PA-6,12), poly(undecanamide) (PA-11),

polylauryl lactam (PA-12),

polydodecamethylene dodecanediamide (PA-12,12).

The PAs have a molecular weight Mn generally greater than or equal to 5,000. Their limiting viscosity (measured at 20°C for a 0.5 g sample in 100 g meta-cresol) is generally greater than 0.7.

PA in the meaning according to the invention must also be understood to mean mixtures of polymers containing at least 50% by weight of the above-described polyamides, where the matrix phase consists of polyamide.

Examples of mixtures include mixtures of aliphatic polyamides and semi-aromatic and/or amorphous polyamides, such as those described in EP 550,308, as well as PA/polyolefin mixtures and especially those described in EP 342. 066 .

According to the invention, PA must be understood to mean polyamide-based thermoplastic elastomers (TPE) which are block copolymers, also known as polyether amides, whose sequence consists of polyamide and crystallizable flexible sequences consisting of polyether.

As softener (V) can be mentioned those which can be incorporated into the mixture according to the invention such as butylbenzenesulfonamide (BBSA), ethylhexyl p-hydroxybenzoate (EHPB) or decahexyl p-hydroxybenzoate (DHPB).

In general, the plasticizers have a disadvantage that they seep

more or less quickly (a few days to a few months) of the polymeric material in which they are incorporated and thus result in fluid loss and dimensional variations in the material.

The mixtures according to the invention which are plasticized, i.e. in which (V)>0, have a further advantage, compared to polyamide-based mixtures containing only plasticizer (V), but which contain neither terpolymers (II) nor copolymers (III), in that they have a corresponding flexibility for a lower level of plasticizer and thus reduced secretion and better dimensional stability.

The above-mentioned mixtures can be obtained by any known mixing technique of the components in a molten state, such as for example extrusion or mixing using a single or twin screw extruder or coelerator or any continuous or batch technique, such as for example using a internal mixer.

The present invention also relates to a use of the mixture in the production of extruded materials, in particular disposable tubes. The obtained materials or articles, especially pipes, films, sheets, fibers and the like are translucent and have good mechanical and chemical properties, such as good flexibility.

Among all the conventional conversion methods used within the thermoplastics industry, which are suitable for the production of articles based on mixtures according to the invention, extrusion techniques can be particularly mentioned.

The materials obtained by extruding the mixtures according to the invention, for example pipes, have a smooth surface condition and their translucency is therefore not disturbed by surface defects.

The extrudability of the mixture according to the invention during their conversion is significantly better than the extrudability of PA-based mixtures which do not simultaneously contain the terpolymer(s) (II) and the copolymer(s) (III). In practice, this improved extrudability will show itself as a reduced extrusion temperature (of the order of 30°C), with a corresponding behavior of the molten product and with a corresponding appearance of the tube.

In the event that the mixture is based on plasticized PA, (V)>0, the expression "better extrudability" will appear at extrusion temperatures corresponding to those of plasticized PA containing neither the terpolymer(s) (II) nor the copolymer(s) (III).

The following examples illustrate the invention.

Example 1

The extrusion is carried out in a twin screw extruder or in a coelter, in the form of rods which are then granulated, from a mixture comprising

<*> 70% by weight PA-11 softened with 12% by weight BBSA, with an intrinsic viscosity in the range 1-1.2 and with a melting temperature in the range 176-183°C, <*> 25% by weight ethylene-BA-maleic anhydride terpolymer with a molar composition of 94.4/4.6/1 and with a melt index equal to 4.5 g/10 min., determined according to NFT standard 51-016 (190°C, load 2.16 kg), and <*> 5% by weight copolymer of ethylene and of MA with a molar composition of 94.4/5.6 and with a melting index of 0.3 g/10 min., determined according to NFT standard 51-016 (190°C, load 2.16kg).

The flexural modulus, discharge and translucency of the mixture thus obtained were determined.

The flexural modulus was determined according to ISO standard 178, for comparison the flexural modulus of the corresponding PA alone was also given.

Excretion was determined as the weight loss of a sample after 30 days in an air-ventilated oven at 120°C.

The translucency was determined as light transmission at 700 nm through a sheet of thickness 1 mm. A light transmission greater than 15% is considered acceptable and particularly advantageous when it is greater than 30%.

This mixture was then extruded in the form of tubes with an inner diameter of 6 mm and an outer diameter of 8 mm using an extruder equipped with a) screw adapted to extrude softened PA with a diameter of 60 mm and with a length/ diameter ratio of 24, b) nozzle coated with chrome or nickel. The extrudability was determined by determining the ease with which the extrusion of the tube could be carried out (behaviour of the molten mass, the size of the diameter of the tube, not breaking) and by determining the maximum temperature of the extrusion temperature curve, necessary to obtain a tube with good appearance (smooth surface appearance). Extrudability is described as "poor" when the tube has a poor surface appearance and/or when the conversion process is poorly controlled and/or the temperature curve required to obtain a tube with a good appearance is too high.

The results are reproduced in table 1.

Example 2a and 2c (comparison)

For comparison, tubes of identical dimensions as described in Example 1 extruded from PA-11

a) containing different levels of plasticizer (28-35% by weight) with limit viscosity in the range 1.1 and 1.4

and with a melting temperature in the range 170-176°C

(example 2a)

b) containing the same level of plasticizer as described in example 1, but with limit viscosity in

advice 1.4 and 1.6 (example 2b)

c) not containing plasticizers and with a limiting viscosity in the range of 1.3 and 1.6 and with a melting temperature of

the range 183-187°C (Example 2c).

The bending modulus, extrusion and translucency of the thus produced PA-11 samples, as well as the extrudability of tubes were determined. The results are reproduced in table 1.

Examples 2d- 2f (comparison)

For comparison, the following mixtures were extruded and formed into tubes of the same dimensions as described in Example 1:

d) a mixture (Example 2d) comprising:

<*> 70% by weight of the same PA-11 as stated in

example 1 (plasticized with 12 wt% BBSA),

<*> 30% by weight ethylene-BA-maleic anhydride terpolymer with the molar composition 94.4/4.6/1 and with a melt index of 4.5 g/10 min., determined according to NFT standard 51-016 (190°C, load 2.16 kg),

e) a mixture (Example 2e) comprising

<*> 70% by weight of the same PA-11 as shown in Example 1 (softened with 12% by weight BBSA) <*> 30% by weight ethylene-BA-maleic anhydride terpolymer with a molar composition of 88.2/11.5/0.3 and a melt index equal to 7 g /10 min., determined according to NFT standard 51-016 (190°C, belasting 2.16 kg),

f) a mixture (Example 2f) comprising

<*> 70% by weight of the same PA-11 as shown in example 1, softened with 12% by weight BBSA) <*> 30% by weight ethylene maleic anhydride copolymer with molar composition 94.4/5.6.

Flexural modulus, extrusion and translucency of the obtained samples based on PA-11, as well as the extrudability of the obtained tubes were determined. The results are reproduced in

table 1.

Example 3

A comprehensive mix

<*> 70% by weight PA-12 softened with 12% by weight BBSA and with an intrinsic viscosity in the range 1.3-1.7 and a melting temperature in the range 168-174°C, * 25% by weight ethylene-BA-maleic anhydride terpolymer with molar composition 94.4/4.6/1 and with a melt index of 4.5 g/10 min., determined according to NFT standard 51-016 (190°C, load 2.16 kg), <*> 5% by weight copolymer of ethylene and of MA with molar composition 94.4/5.6 was extruded and shaped like a tube with the same dimensions as described in example 1.

The flexural modulus, extrusion and translucency of the thus extruded sample of PA-12, as well as the extrudability of the tube obtained, were determined. The results are reproduced in table 1.

Example 4 (comparison)

For comparison, a mixture comprising <*> 75% by weight PA-12 with the same properties as stated in Example 3 (containing the same level of BBSA), <*> 25% by weight ethylene-polyethylene-maleic anhydride elastomeric copolymer mEPR comprising 0.4-0.8 wt% maleic anhydride, which mixture was extruded and formed into a tube of the same dimensions as described in Example 1.

The flexural modulus, extrusion and translucency of the thus extruded sample of PA-12, as well as the extrudability of the tube obtained, were determined. The results are reproduced in table 1.

Example 5 (comparison)

For comparison, a mixture was prepared extensively

<*> 70% by weight unplasticized PA-6, whose melting temperature was in the range 217-223°C, <*> 25% by weight ethylene BA-maleic anhydride terpolymer with a molar composition of 94.4/4.1/1 and with a melting index equal to 4.5 g/ 10 min., determined according to NFT standard 51-016 (190°C, load of 2.16 kg), <*> 5% by weight copolymer of ethylene and of MA with molar composition 94.4/5.6 and extruded and shaped as a tube with the same dimensions as described in example 1.

The flexural modulus, extrusion and translucency of the thus extruded sample of PA-6, as well as the extrudability of the tube obtained, were determined. The results are reproduced in table 1.

Claims (5)

1. Translucent and flexible mixture based on polyamide resin comprising: (A) 50-95% by weight 1) of at least one polyamide resin (I), and 2) various additives (IV) such as stabilizers, mold release agents, lubricants, crystallization accelerators, pigments, organic and/or inorganic fillers or colors and antioxidants, and 3) possibly at least one plasticizer (V) in an amount of up to 50% by weight calculated on (A) and preferably less than 20% by weight calculated on (A ), (B) 5-50% by weight and preferably 10-50% by weight of (a) at least one ethylene alkyl (meth)acrylate - unsaturated dicarboxylic acid anhydride terpolymer (II), and (b) at least one ethylene alkyl (meth)acrylate copolymer (III), where 1/30 <. (b)/(a) < 2 and preferably (b) / (a) > 2/3 and such that its flexural modulus, determined according to IOS standard 178, is less than or equal to 2/3 of the flexural modulus of the PA resin (I ) alone and is less than 750 MPa and advantageously less than or equal to 1/3 of the flexural modulus of the polyamide resin (I) alone and less than 500 MPa, characterized in that the polyamide resin (I) has a light transmission at 700 nm which is greater than 15% and preferably greater than 30%, through a sheet with a thickness of 1 mm. 2. Mixture according to claim 1, characterized in that it is based on polyamide-11, polyamide-12 and/or polyamide-12,12. 3. Mixture according to claim 1 or 2, characterized in that the alkyl (meth)acrylic units from which the terpolymers (II) and/or the copolymers (III) are derived are selected from methyl, ethyl, n-butyl, isobutyl, 2 -ethylhexyl and cyclohexyl acrylates and methyl and ethyl methacrylates and advantageously from ethyl acrylate (EA), n-butyl acrylate (BA) and methyl acrylate (MA). 4. Mixture according to claims 1-3, characterized in that the unsaturated dicarboxylic anhydride from which the terpolymers (II) are derived is a maleic anhydride. 5. Use of the mixture according to claims 1-4 in the production of extruded materials, especially single-layer pipes.