EP0811038A1

EP0811038A1 - Composition including a fluoroelastomer and a thermoplastic polyamide, and resulting film

Info

Publication number: EP0811038A1
Application number: EP96943166A
Authority: EP
Inventors: Régis Jacquemet; Jean-Jacques Labaig; Joachim Merziger
Original assignee: Elf Atochem SA
Current assignee: Arkema France SA
Priority date: 1995-12-22
Filing date: 1996-12-20
Publication date: 1997-12-10
Also published as: WO1997023570A1; AU1198597A; CA2211806A1; CN1102616C; KR19980702401A; US5986005A; JPH11501083A; CN1182449A; KR100312055B1

Abstract

A modifying agent composition, a masterbatch and a final composition including a fluoroelastomer and a thermoplastic polyamide, as well as a film made from the final composition, are disclosed.

Description

COMPOSITION COMPRISING A FLUOROELASTOMER AND A THERMOPLASTIC POLYAMIDE AND FILM OBTAINED

Description

The subject of the present invention is a composition comprising a fluoroelastomer and a thermoplastic polyamide. Intended to improve the processing of plastics. Another subject of the invention relates to a composition based on hydrocarbon polymers comprising a fluoroelastomer and a thermoplastic polyamide. The present invention further relates to a homogeneous thermoplastic film having improved optical and mechanical properties and comprising modifying agents such as a fluoroelastomer and a thermoplastic polyamide. It is generally accepted that during the extrusion of a plastic material, flow irregularities appear at the outlet of the die when a critical shear rate is exceeded. Below, the extrudates are smooth so that ^* above the critical rate is observed for surface defects. These so-called "melt fracture" defects come in several forms. At a shear rate slightly higher than the critical rate, the films obtained by extrusion blow-molding lose their transparency and their gloss. For markedly higher rates, which correspond to higher productivity, homogeneity defects with smooth areas in a rough surface appear. These defects significantly reduce the optical and mechanical properties of the film. The same phenomena can be observed on extruded rods. When the surface of the rods loses their shine and becomes dull and rough, it is often compared to an "orange peel".

Among the various solutions proposed to remedy this drawback, the use of modifying agents is of greater industrial interest. Thus in US Pat. No. 3,334,157, the incorporation of polytetrafluoroethylene improves the optical properties of the polyethylene film. According to US Patents 4,855,360 and US 5,015,693, a fluoroelastomer in combination with a polyoxyalkylene are used to improve the transformation of hydrocarbon polymers. Organophosphates or organophosphites in combination with a fluoroelastomer have been described in US Patents 4,983,677 and US 4863983 to also improve the transformation of hydrocarbon polymers

However, additives such as anti-blocking agents, fillers, pigments, dyes and stearates, which are essential for the transformation of plastics, interact with these fluoroelastomers and significantly reduce their effectiveness. In an attempt to overcome this drawback, a process consisting of first to treat the extruder die with modifying agents and then to transform plastics has been described in patent WO 9105007. The modifying agent used contains a functionalized fluorinated copolymer comprising tetrafluoroethylene units and a functional group containing a fluorinated monomer This process has the disadvantage of being in two stages.

A composition has now been found which improves the transformation of plastics, during their processing by extrusion, without however having the drawbacks set out above. This composition comprising a fluoroelastomer and a thermoplastic polyamide, forms the subject of the present invention

The present invention not only makes it possible to move the “melt fractures” towards high shear rates but also to obtain homogeneous films with a reduced duration of setting in operation of the extruder.

The present invention therefore provides a composition of modifying agents for improving the transformation of plastics, characterized in that it comprises

(a) a fluoroelastomer and (b) a thermoplastic polyamide

Thermoplastic polyamides are polymers with polyamide blocks and polyether blocks

Polymers with polyamide blocks and polyether blocks result from the copolycondensation of polyamide blocks with reactive ends with polyether blocks with reactive ends, such as, inter alia ^•

1) Polyamide sequences with diamine chain ends with polyoxyalkylenated sequences with dicarboxylic chain ends. 2) Polyamide sequences at the ends of dicarboxylic chains with polyoxyalkylenated sequences at the ends of diamine chains obtained by cyanoethylation and hydrogenation of polyoxyalkylene alpha-omega dihydroxylated aliphatic sequences called polyetherdiols. 3) Polyamide sequences at the ends of dicarboxylic chains with polyetherdiols, the products obtained being, in this particular case, polyetheresteramides

The polyamide sequences with dicarboxylic chain ends originate, for example, from the condensation of alpha-omega aminocarboxylic acids of lactams or of dicarboxylic acids and diamines in the presence of a chain-limiting dicarboxylic acid. The polyamide blocks are advantageously made of polyamide- 12_or in polyamide- 6

The number-average molar mass Mn of the polyamide blocks is between 300 and 15,000 and preferably between 600 and 5,000 The mass Mn of the polyether blocks is between 100 and 6,000 and preferably between 200 and 3,000

Polymers with polyamide blocks and polyether blocks can also comprise randomly distributed units. These polymers can be prepared by the simultaneous reaction of the polyether and of the precursors of the polyamide blocks.

For example, polyetherdiol, a lactam (or an alpha-omega amino acid) and a chain-limiting diacid can be reacted in the presence of a little water. A polymer is obtained which essentially has polyether blocks, polyamide blocks of very variable length, but also the different reactants which reacted randomly which are distributed statistically along the polymer chain

These polymers containing polyamide blocks and polyether blocks, whether they originate from the copolycondensation of polyamide and polyether blocks prepared beforehand or from a reaction in one step, exhibit, for example, shore D hardnesses which may be between 20 and 75 and advantageously between 30 and 70 and an intrinsic viscosity between 0.8 and 2.5 measured in metacresol at 250 ° C for an initial concentration of 0.8 g / 100 ml

Whether the polyether blocks are derived from polyethylene glycol, polyoxypropylene glycol or polyoxytetramethylene glycol, they are either used as such and copolycondensed with polyamide blocks having carboxylic ends, or they are aminated to be transformed into polyether diamines and condensed with polyamide blocks to carboxylic ends They can also be mixed with polyamide precursors and a chain limiter to make polymers with polyamide blocks and polyether blocks having randomly distributed units Polymers with polyamide and polyether blocks are described in US Patents 4,331,786, US 4,115,475, US 4,195,015, US 4,839,441, US 4,864,014, US 4,230,838 and US 4,332,920.

The polyether may for example be a polyethylene glycol (PEG), a polypropylene glycol (PPG) or a polytetra methylene glycol (PTMG). The latter is also called polytetrahydrofuran (PTHF).

Whether the polyether blocks are in the polymer chain with polyamide blocks and polyether blocks in the form of diols or diamines, they are called for simplification PEG blocks or PPG blocks or even PTMG blocks. It would not be departing from the scope of the invention if the polyether blocks contained different units such as units derived from ethylene glycol, propylene glycol or even tetramethylene glycol.

Preferably, the polymer with polyamide blocks and polyether blocks comprises a single type of polyamide block and a single type of polyether blocks. Advantageously, polymers with PA-12 blocks and PEG blocks are used, polymers with PA-12 blocks and PTMG blocks and polymers with PA-6 blocks and blocks.

PEG.

Advantageously, the polymer with polyamide blocks and polyether blocks is such that the polyamide which is in the form of blocks and that which is optionally distributed statistically in the chain, represents 50% by weight or more of the polymer with polyamide blocks and polyether blocks. Advantageously, the amount of polyamide and the amount of polyether are in the ratio (polyamide / polyether) 2/3 to 3/1 and preferably close to 1/1.

The polymer containing polyamide blocks and polyether blocks having hydrophilic properties is particularly preferred, that is to say that having PEG blocks or whose polyether blocks have a majority of units derived from ethylene oxide.

Thus the films of the invention are antistatic.

The fluoroelastomers can be in the form of powder or granules. They are generally homopolymers or copolymers of fluorinated olefins whose fluorine / carbon ratio is greater than or equal to 0.5. A fluorine / carbon atom ratio close to 1 is particularly preferred.

Among the homopolymers, mention may be made of polyvinylidene fluoride or polyvinyl fluoride. The advantageously chosen copolymers are derived from vinylidene fluoride and one or more fluorinated olefins.

Particularly preferred fluoroelastomers are copolymers of vinylidene fluoride and propylene hexafluoride. Advantageously the copolymers containing more than 50 mol% of vinylidene fluoride are used

According to the invention, it is possible either to use the compositions of modifying agents as such or to dilute them in a polymer or a mixture of polymers to form masterbatches. The masterbatch advantageously consists of a plastic material of the same type as that which it is desired to modify, and the fluoroelastomer and the polyamide are incorporated therein. The term “plastic material of the same type” means materials comprising essentially the same monomers in similar proportions. The polymers whose viscosity is close to that of the plastic material to be extruded are particularly preferred.

These masterbatches can also contain fillers, in particular antioxidants (in the following, unless indicated otherwise, the% are by weight).

The dilution of the modifying agent compositions is such that the content of fluoroelastomer in these masterbatches is generally greater than

0.1% and preferably between 0.3% and 5% by weight and the content of thermoplastic polyamide is generally greater than 0.1% and preferably

0.3 to 20%.

These masterbatches can be used to pre-treat the output die of the extruders or mix them with the plastics to be transformed before or during the processing.

Another subject of the invention is the final compositions comprising a fluoroelastomer, a thermoplastic polyamide and the plastic to be extruded. They can also contain anti-blocking agents, for example silica, pigments such as titanium dioxide and stearates.

By plastic material is meant polymers comprising olefin units such as for example ethylene, propylene, butene-1 units, etc. By way of example, there may be mentioned:

- polyethylene, polypropylene, copolymers of ethylene with alphaolefins. These products can be grafted with anhydrides of unsaturated carboxylic acids such as maleic anhydride or unsaturated epoxides such as glycidyl methacrylate. - copolymers of ethylene with at least one product chosen from (i) unsaturated carboxylic acids, their salts, their esters, (ii) vinyl esters of saturated carboxylic acids, (iii) dicarboxylic acids unsaturated, their salts, their esters, their hemiesters, their anhydrides (iv) the unsaturated epoxides

These ethylene copolymers which can be grafted with anhydrides of unsaturated dicarboxylic acids or unsaturated epoxides - optionally maleylated styrene / ethylene-butene / styrene block copolymers

Mixtures of two or more of these polyolefins can be used.

We use advantageously

- polyethylene, - copolymers of ethylene and an alpha-olefin and preferably low density copolymers (LDPE) and better still linear low density copolymers (LLDPE),

- copolymers of ethylene / of an alkyl (meth) acrylate,

- copolymers of ethylene / of an alkyl (meth) acrylate / of maleic anhydride, maleic anhydride being grafted or copolymerized,

- copolymers of ethylene / of an alkyl (meth) acrylate / of glycidyl methacrylate, the glycidyl methacrylate being grafted or copolymerized,

- Polypropylene The amount of fluoroelastomer present in the final composition can be greater than 10 ppm and preferably between 100 ppm and 1000 ppm.

The amount of thermoplastic polyamide present in the final composition can vary within wide limits. It is generally between 10 ppm and 5% and preferably between 100 ppm and 1%. The final compositions according to our invention can be transformed by any known means, for example injection, extrusion, extrusion blow molding of hollow bodies and extrusion blow molding of sheath

Another object of the invention relates to a thermoplastic film obtained by extrusion blow molding of the final compositons described above. This homogeneous film. Having improved optical and mechanical properties is characterized in that it comprises a fluoroelastomer and a thermoplastic polyamide. besides the advantage of being antistatic

The film according to the invention can be obtained for a period of warm-up of the extruder of less than 2 hours, preferably for a period of less than or equal to one hour.

The following examples illustrate the invention without limiting it The plastic material used is LDPE LL0209 AA from BP linear low density polyethylene which is a copolymer comprising butene units and predominantly ethylene units with an Ml (Melt Index) at 2.16 kg and 190 ° C. = 0, 9 and a Density = 0.92

KYNAR 2821 = copolymer comprising 88% by weight of vinylidene difluoride and 12% by weight of propylene hexafluoride

PEBAX M. thermoplastic polyamide consisting of PA-12 blocks of Mn = 1,500 and PEG blocks of Mn = 1,500 and shore hardness D 40. The masterbatches are obtained either by mechanical mixing of the various modifying agents, additives and polymers, or by mixing in a BUSS PR 46/70 1 1 mixer. In this case the temperature profile is 170 ° C - 195 ° C - 200 ° C and the die temperature is equal to 210 ° C.

The masterbatches are then diluted in LDPE LL0209AA by simple mechanical mixing with the optional addition of additives to give the final compositions

The modifiers in the final compositions were evaluated using two types of extruder a) The HAAKE U HAAKE RHEOLEX extruder has a screw diameter equal to 30 mm and an active screw length equal to 25 times its diameter. The compression ratio of the extruder is equal to 3. The diameter of the die is 3 mm and its length is equal to 3 times its diameter The angle at the inlet of the die is 180 °. The temperature profile of the extruder

190 ° C - 200 ° C - 210 ° C - 220 ° C - 225 ° C is constant for all the tests Likewise for the die temperature which is equal to 215 ° C.

b) The KAUFMAN extruder

The KAUFMAN extruder transforms the final compositions by extrusion blow molding of sheath. The characteristics of the extruder and of its die are given in table 1. The different zones of the extruder screw are presented in table 2. The temperature profile of the different zones recorded in table 3, is constant for all attempts.

Table 1 - Characteristics of the KAUFMAN line

Table 2 - Areas of the KAUFMAN screw

Table 3 - KAUFMAN line temperature profile

The optical and mechanical properties of the film obtained by sheath extrusion-blowing are then evaluated using the LUMAQUITAINE test and the DART TEST respectively. The LUMAQUITAINE test consists in forming, through a system of lenses, the image of the fixed slit of a collimator, illuminated by a light source This image is received on a window of transparent sinusoidal or "test pattern" associated with a photometer recorder A film test piece having a circular useful part of 20 mm in diameter is placed in a sample holder which can be rotated, located on the optical axis of the system between the collimator and the target, in a parallel beam of light

The variation curve of the intensity of the transmitted light modulated by the displacement of the target is recorded

If M in millimeters is the distance separating the baseline from the maxima and m in millimeters is the distance separating the baseline from the minima of the corresponding sinusoidal curve, the contrast factor making it possible to determine, for each number of waves, the attenuation due to the film is given by the following formula

C o / ₀ = M - m _{X 1 0} QM + m

The DART TEST is a method consisting in determining the energy necessary for the impact rupture of a plastic film, under the effect of a punch of mass less than or equal to 300g falling in free fall from a height 66 cm The mass of the projectile is determined for which 50% of the test pieces

(At least 10) of the same tested sample are broken under the conditions described in the previous paragraph

The mass of the projectile is defined as the mass of the punch increased by the additional masses and the mass of the clamping collar of these masses

The mass of the projectile is varied so as to obtain both broken test pieces and intact test pieces in the same group of 10 test pieces and with at least 3 different rupture rates between 0% and

100% The impact breaking mass Wf of the film is expressed in grams according to the formula below

W _f = W | - ΔW [S / 100 - 0.5] OR

W | is the lowest used projectile mass (in grams) for which all the test pieces are broken

ΔW is the increase in mass used successively from one test to another (in grams)

S is the sum of the percentages of ruptures for each mass of projectile (this sum includes the percentages corresponding to all the masses of projectile used from the mass corresponding to no rupture up to the mass W | inclusive)

The antistatic properties of the film are evaluated by a method based on the ability of a surface to run off static charges. This method consists first of all in charging the film surface for a few seconds via a high voltage After cutting from the high-voltage source, note the half-discharge time, which is the time necessary to go from the maximum potential V _max reached to half this value V _max / 2 An antistatic material will more easily discharge the charges and therefore the half-discharge time will be shorter b) Conduct of the tests (i) Stabilization of the extruder with LDPE LL0209AA,

(n) Start I ^* extrusion with the final compositions (m) Taking extrusion parameters and sample -a) extruder HAAKE RHEOLEX pressure and temperature I 'inlet of the die the torque value, the flow and inflation for different rotation speeds (20 to 80 revolutions / min) -b) KAUFMAN extruder pressure before and after the filters (bar) die temperature (° C) intensity (A) cooling speed (%) and speed of draw (m / min) at the start of the test and after each hour

(iv) Purging the HAAKE RHEOLEX extruder using PEbdl LL0209 AA Dismantling and cleaning the die in an acetone bath

- Purge of the KAUFMAN extruder using POLYBATCH KC30 from SCHULMAN (polyethylene-based masterbatch comprising 50% by weight of additives and a density = 1.38) with Ml at 2.16 kg and 190 ° C. = 1, 3 - Purge of the sheath and of the KAUFMAN die using crystal polystyrene LACQRENE 1260 with an Ml at 5 Kg and 200 ° C = 4 and a density = 1.05

(v) The extruder is ready for a new test

For all the tests carried out on the KAUFMAN extruder, the speed of rotation of the screw is 35 revolutions / min, a drawing speed = 8.5 m / min and the extruder is adjusted to give:

A film width = 500 mm A film thickness = 50 μm

Example 1

A final composition is used containing only the plastic material (PEbdl LL0209AA) to be transformed.

This final composition is transformed into a rod using the HAAKE RHEOLEX extruder. The parameters and samples (table 4) were taken one hour after starting the extrusion at a screw rotation speed of 20 revolutions / min and at a die temperature equal to 215 ° C.

A film is obtained by the extrusion blow molding of sheath using the KAUFMAN extruder. The appearance of the rods and film thus obtained is shown in Table 4.

Example 2

A masterbatch of the following composition is diluted at a rate of 2%: PEbdl LL0209 AA powder = 97.9% KYNAR 2821 = 2.0%

IRGANOX B 900 (antioxidant agent) = 0.1% in the plastic material (PEbdl LL0209 AA) to be transformed. The final composition thus obtained contains:

LDPE LL0209 AA powder = 99.958% KYNAR 2821 = 0.04%

IRGANOX B 900 (antioxidant) = 0.002% This final composition is transformed in an identical manner to Example 1.

Example 3 A final composition is prepared in the same way as in Example 2 except that I add 2% of MMF15C from SCHULMANN containing about 15% of natural silica.

The final composition contains: LDPE LL0209 AA powder = 99.658%

KYNAR 2821 = 0.04%

IRGANOX B 900 (antioxidant) = 0.002% Silica = 0.3% The final composition is transformed in an identical manner to Example 2

Example 4

A final composition is prepared in an identical manner to Example 3 except that 2% of MMF15C is replaced by 4% of MM CMPF 59080 of SYNTHECOLOR containing 2% of anti-slip agent ERUCAMIDE The final composition contains

LDPE LL0209 AA powder = 95.958

KYNAR 2821 = 0.04%

IRGANOX B 900 (antioxidant) = 0.002% MM CMPF 59080 = 4% The final composition is transformed in an identical manner to example 2

w

Ut

Table 4

not

H

O KJ o tn o

Example 5

The final composition of Example 2 is taken up again and its behavior as a function of time is studied during the extrusion blow molding process on the KAUFMAN extruder. The parameters noted and the appearance of the film obtained are shown in Table 5.

Example 6

Examples 6 to 8 were carried out on the KAUFMAN extruder. MM 29790 PG = antioxidant (SANTONOX)

A final composition is prepared from a masterbatch containing LDPE LL0209 AA (granules) 97.7% KYNAR 2821 2.0%

MM 29790 PG 0.3% which is diluted at a rate of 2% in the plastic material (PEbdl LL0209

AA) to be transformed and to which 2% of SCHULMANN MMF15C has been added. The final composition thus obtained contains

PEbdl LL0209 AA 97.954%

Silica 0.3% KYNAR 2821 0.04%

MM 29790 PG 0.006%

PE (polyethylene) 1.7%

Example 7 The procedure is identical to Example 6 except that the masterbatch used additionally contains 4% of PEBAX M. The final composition contains

PEbdl LL0209 AA 97.874%

Silica 0.3% PEBAX M 0.08%

KYNAR 2821 0.04%

MM 29790 PG 0.006%

PE (polyethylene) 1.7%

Example 8

The procedure is identical to that in Example 7 except that the masterbatch contains 8% of PEBAX M instead of 4%. The final composition contains PEbdl LL0209 AA 97.794%

Silica 0.3%

PEBAX M 0.16%

KYNAR 2821 0.04%

MM 29790 PG 0.006%

PE (polyethylene) 1.7%

The optical and mechanical properties of the film obtained, as a function of the operating time of the extruder, are shown in Tables 6 and 7 respectively. The PE (polyethylene) comes from the masterbatches MM F 15C and MM

29790 PG.

Table 6

Breaking mass at 50% (g)

Example 6 Example 7 Example 8 Example 8 Extruder

(hours)

0 174 174 174

1,174 188,191

2,183,187,192

3 190 193 193

Table 7

By taking the parameters to obtain the contrast factor at different points (25) of the film obtained by sheath extrusion-blowing of the final compositions of Examples 6 to 8, we can deduce the homogeneity of the

Thus, Tables 8 and 9 show that the film obtained by extrusion blow molding of a final composition comprising a fluoroelastomer and a thermoplastic polyamide is more homogeneous than a film obtained by transformation of a final composition comprising a fluoroelastomer alone.

Table 8 Homogeneity of the film after one hour of operating the extruder

Table 9 Homogeneity of the film after two hours of operating the extruder

Furthermore, the antistatic character of the film obtained from the compositions of Examples 6 and 8 was evaluated according to the method described above. Thus, the half-discharge time of the film from Example 6 is 169 seconds, while a composition of LDPE comprising 400 ppm of KYNAR and 1600 ppm of PEBAX (Example 8) results in a film whose half-time charge reduced to 18 seconds

Claims

1. Composition of modifying agents for improving the transformation of plastics, characterized in that it comprises:

a a fluoroelastomer b a thermoplastic polyamide

2. Composition according to claim 1 in which a is a copolymer containing more than 50 mol% of vinylidene fluoride and b is a polymer with polyamide blocks and polyether blocks.

3. Composition according to any one of the preceding claims, in which a and b are diluted in a plastic material the content of a being between 0.3 and 5%, the content of b being between 0.3 and 20%, these percentages being by weight of the whole plastic material and a and b.

4. Composition according to any one of the preceding claims, in which the plastic material to be transformed is a homo or copolymer polyethylene.

5. Plastic film containing the modifiers of any one of the preceding claims.

6. Film according to claim 5 obtained by blown coextrusion.