ES2249969B1 - PVC BASED BLENDS WITH HIGHER TEMPERATURE OF VICAT COATING AND IMPROVED PROCESSABILITY. - Google Patents

Abstract

PVC-based mixtures with higher Vicat softening temperature and improved processability, comprising between 10 and 95% by weight of PVC-based resin, between 2.5 and 87.5% by weight of a compound capable of producing an increase in PVC TVICAT at mix it with it, and between 2.5 and 70% by weight of a third component, which modifies the mechanical properties and / or viscosity.

Description

PVC-based mixtures with a higher temperature of Vicat softening and improved processability.

Field of the Invention

The invention relates to mixtures Polymers based on polyvinyl chloride (PVC) good dimensional stability at high temperatures, at time that processability is improved, maintaining values of ductility and impact resistance similar to those presented by PVC resin without mixing.

Background of the invention

Polyvinylchloride is a material. polymer of wide commercial use, since it occupies the second place within the most used polymeric materials, and the first in construction and interior equipment, applications in which reaches 50% of the total polymers used in the same. Its use is widespread, being used mostly (65%) in long-term applications such as tubes, windows, cables, blinds, etc. It is also used in medium and short duration applications, such as appliances, toys, hoses, bottles, packaging film, etc ..., which It represents about 35% of total PVC consumption.

Despite its high market share, since its origins were found that the PVC resin presented serious limitations due to the difficulty of processing and high thermal degradability In order to correct these bad properties the need to incorporate into its formulation was detected a series of additives of different types, such as stabilizers thermal, plasticizers, lubricants, impact modifiers, flame retardants, fillers and pigments, among others. The addition of such additives, in varying amounts, has converted to PVC in a very versatile material, since the great diversity of possible formulations allow you to adapt to applications and demands from many different market areas; so in their applications covers a very wide range of requirements, which goes from a rigid high modulus material to high plastisols flexibility, going through a whole range of intermediate states whose behavior depends on the additives added.

Despite the above and its high share of market, PVC presents a serious limitation due to its relatively low service temperature. PVC compounds rigid commercially available have a temperature of thermal distortion (HDT) of the order of 75-80ºC, which which entails a lack of rigidity above that temperature. The effects associated with the thermal softening of PVC a high temperatures generally go along the line exhibited by other thermoplastics. Thus, for example, there is a decrease of the module and the tension, while the extensibility and creep increase, as do permeability and susceptibility to chemical agents.

Many items in which it is used or is I could use PVC, as electrical accessories (some of These accessories, such as the power strips, are subjected to deformation resistance tests, introducing them in an oven at 100ºC for 1 hour) and computer among others, are subjected to high temperatures by the mere use of the equipment in question, which quite limits the PVC application due to its low stiffness at elevated temperatures or moderate. A field in which PVC has a great use It is in the construction sector. Are currently appearing new regulations that may limit its use, especially in the sector  of the pipes. PVC compounds are being demanded rigid intended for this purpose that, first, carry a stabilization other than lead and, most importantly, they have a vicat temperature of 5 kg higher than 79ºC (since these pipes could lead hot liquids).

Therefore, it can be concluded that the low thermal distortion temperature of PVC does not allow its use in many areas of market demand. However, its low cost and great versatility have meant that much of the research effort has focused on resolving this limitation. Thus, in order to solve this problem, various procedures have been published that basically respond to two lines of action. Those based on the chemical modification of the PVC resin by introducing a three-dimensional structure in the linear polymer ( T. Jando, K. Mori, J. Vinyl Technol. 13, 2 (1991); I. Kelnar, M Schatz, J. Appl. Polym. Sci. 48, 669 (1993); M. Hidalgo, L. González, C. Mijangos, J. Appl. Polym. Sci. 61, 1251 (1996); B. Saethre, M. Gilbert, Polymer 37, 3379 (1996)), and the technology - based mixtures (Patterson JR, CS Cinoman, DL Dunkelberger, Ang. Makr Chem. 171, 175 (1989), J. Gao, L. Yang, Li Z, L. Ren, J. Appl. Polym. Sci. 59, 1787 (1996); R. Flores, Pérez, P. Cassagnau, A. Michel, JY Cavaillé, J. Appl. Polym. Sci. 60, 1439 (1996) ).

The first method is based mainly on replace chlorine atoms in the chain with bifunctional groups, to obtain a crosslinked polymer of higher HDT. Saying procedure can be carried out during the processing of the material, by reactive processing.

For its part, the second method, based on the mixing technology, consists of mixing the PVC resin with another polymer of higher HDT, and therefore, higher temperature of Vicat softening (called "temperature improver Vicat "), miscible or partially miscible with PVC, to give place for mixtures with an HDT higher than that presented by PVC without Mix. Normally, the addition of said T_ {VICAT} enhancer entails a series of problems, so it becomes necessary add other components to solve them. So, in general, it produces a worsening of impact resistance and ductility below acceptable limits. Also usually produce a worsening of processability or increased melt viscosity. Given the wide demand of the PVC market the resolution of these problems becomes especially important, in order to increase its HDT without worsening dramatically other properties and thus be able to use it in areas of the market currently inaccessible.

Thus, in the literature they cite various acrylic polymers ( D. Hardt, H. Alberts, H. Bartl, DE 2317652 (1974); I. Shiichi, S. Lizuka, JP 05331337 (1993) ), polyesters ( Y. Keisuke, JP 01308618 (1989) ) or rubber modified resins ( S. Takahashi, Y. Makino, H. Kiyota, JP 02110155 (1990) ) as possible PVC modifiers. However, mixtures of more than two components are predominant. Those in which some component is an acrylic copolymer abound ( A. Tamura, O. Noda, JP 08092421 (1996); O. Sodeyama, S. Nagata, IP 9234511 (1993); B. Hamann, P. Volkmann, R. Hohberg, DD 210702 (1984), O. Sodeyama, S. Nagata, JP 05202257 (1993); Y. Aoki, M. Maeda, K. Seki, JP 61143459 (1986); G. Huynh-Ba, US5502111 (1996) ; N Toshito, JP 60139739 (1985) ). Chlorinated PVC ( K Sanjo, T. Hirata, K. Michikado, T. Iwata, N. Matsumura, JP 10014072 (1998); LM Soby, MH Lehr, ED Dickens Jr, M Rajagopalan, W S. Greenlee, US 5354812 ( 1994) ), polyolefins ( B. H Lee, US 4767817 (1988); K. Wada, Y. Mishima, JP 06080835 (1994) ), polycarbonate ( SE Elghani, W. Fischer, M Koehler, J. Lindner, R. Prinz, US 3882192 (1975) ) and crosslinked resins ( H. Yusa, Y. Lizuka, H. Akutsu, FR 2474516 (1981); CF Hammer, FR 2148496 (1973) ) also constitute some of the commonly used modifiers.

The objective pursued in most of the examples found in the literature is reduced to the increase in the Vicat softening temperature without worsening processability; however, there are few examples in the literature ( L. M Soby, ML Lehr, ED Dickens Jr, M Rajagopalan, WS Greenlee, US 5354812 (1994)) in which, in addition to the aforementioned point, special emphasis is placed on improvement of processability or reduction of melt viscosity.

Summary of the Invention

The object of the present invention is to obtain mixtures based on polyvinyl chloride with good stability dimensional at high temperatures, mechanical properties, such as ductility and impact resistance, similar to those presented by PVC materials, and flow properties (processability) equal to the initials or improved. It has now been found that mixtures consisting of PVC, a Vicat temperature improver, miscible or partially miscible with PVC, and a component or mixture of components that reduce viscosity and / or improve mechanical properties, meet all the above requirements.

Brief description of the figures

Figures 1 and 2 show the curves of viscosity of unmixed PVC (the PVC compound, called "PVC without mixing" corresponds to a formulation marketed by AISCONDEL) and two mixtures, a ternary mixture PVC,? -methyl stretch copolymer and Acrylonitrile Butadiene Stirene (AMS-ABS) and low density polyethylene (LDPE), of Composition by weight PVC / AMS-ABS / LDPE 100/60/10 (fig. 1), and a quaternary mixture of PVC, polymethyl methacrylate (PMMA), PVC and acrylate graft copolymer (PVC-Acr) and low density polyethylene (LDPE), of Composition by weight PVC / PMMA / PVC-Acr / LDPE 100/50/15/10 (fig. 2). More specifically these figures show the evolution of viscosity (η) versus gradient (γ), which has been measured in a capillary extrusion rheometer at a temperature of T = 170 ° C.

Tables I and II show the properties mechanical mixtures described above and PVC without Mix. Specifically, it presents the temperature values of Vicat softening (T_ {VICAT}), tensile properties and left impact These properties have been measured following the standards UNE 53-118-78, UNE 53-023-86 and UNE 53-193-85, respectively.

Detailed description of the invention

The present invention relates to mixtures polymeric, which include:

- between 10 and 95% by weight of resin based PVC,

- between 2.5 and 87.5% by weight of a compound capable of producing an increase in the T_ {VICAT} of PVC when mixed with it, and

- between 2.5 and 70% by weight of a third component, which modifies the mechanical properties and / or viscosity.

These mixtures have good stability dimensional at high temperatures and similar processability or improved compared to that of PVC.

The PVC usable in this invention can be both a homopolymer and a vinyl chloride copolymer, synthesized by any known polymerization process, such as suspension, mass, solution, emulsion, dispersion and microsuspension processes, but not excluding the rest. Preferably, by a suspension process. In the case of it is a copolymer, the monomer used to obtain thereof may be any monomer copolymerizable with the vinyl chloride. Said copolymerizable monomer includes esters Acrylics, methacrylic esters, monoolefins, diolefins, derivatives of styrene, acrylonitrile, vinyl esters, chloride vinylidene, vinyl ethers and polyfunctional monomers that can give crosslinking, such as allyl methacrylate and phthalate diallyl, the use of ethylene, propylene being preferable, 1-butene, 2-butene, 1-pentene, 1-hexene, isobutylene and vinylidene chloride, all of them in small proportions such that do not affect the Vicat softening temperature of the PVC

Additionally and optionally the PVC can present in its composition any known additive for formulations of PVC Example of such additives, although not limited exclusively to them, they are stabilizers, plasticizers, extenders, lubricants, fillers, pigments, process aids and / or modifiers of impact.

The softening temperature improver Vicat (T_ {VICAT}) usable in the invention is a polymer, copolymer or mixture thereof, miscible or partially miscible with PVC, and that presents a TWCAT measured by the UNE standard 53-118-78, higher than the Rigid PVC compound used. Its function is to increase the T_ {VICAT} of the PVC compound when mixed with it. The T_ {VICAT} enhancers usable in the invention are acrylic polymers, preferably copolymers of α-methyl styrene and Acrylonitrile Butadiene Stirene (AMS-ABS), copolymers Acrylonitrile Butadiene Stirene (ABS) and polymethyl methacrylate (PMMA). In case of a copolymer, the monomers that form it can be part of the Same in any proportion.

In general, the addition of a booster T_ {VICAT} represents an improvement in the dimensional stability of PVC at high temperatures to the detriment of processability and mechanical properties thereof. Therefore, in order to correct said problem, the mixture of the invention consists of a third component. The third component usable in the invention is a polymer, copolymer or any combination thereof, whose function is to reduce melt viscosity and / or improve mechanical properties that the binary mixture would obtain, PVC + T_ {VICAT} improver.

Thus, the third component usable in the invention can be any type of polyethylene, linear or branched, ethylene vinyl acetate copolymer (EVA) modified or unmodified, polycaprolactone, polylactone, polylaurillactone and acrylate based copolymer.

In the case of branched polyethylene, understand that it can be any type and quantity of branch. At In the case of the EVA copolymers, it is understood that it comprises from 10% up to 80% by weight of vinyl acetate and from 20% up to 90% by weight of ethylene. In the case of an EVA copolymer modified, it is understood that it can be modified with any chemical compound, preferably carbon monoxide (CO), but without excluding others. In the case of an acrylate based copolymer, preferably, a PVC copolymer with polyacrylate The copolymer can be any type of copolymer such as, but not excluding others, graft, block, random or alternating. Regarding its composition, the Acrylate percentage can be 5 to 95%.

The mixture of the invention has a Vicat softening temperature, measured according to the UNE standard 53-118-78, higher than the Rigid PVC compound, which results in stability dimensional at high temperatures improved with respect to it. So it shows a melt viscosity similar to or less than of the rigid PVC compound and, therefore, an improvement in processability that will manifest itself in industrial processes such as extrusion, injection and others. On the other hand, the properties mechanical, such as resistance and breakage deformation, despite suffer a slight worsening, they are within the range of properties usually required by the applications of the rigid PVC compounds and, therefore, within the limits of use of this type of materials.

The following details the invention based on some examples, without any limitation of the scope of the invention.

Examples Example 1 Rheological and mechanical properties of a ternary mixture based in PVC

A ternary mixture of a polyvinylchloride compound (PVC), copolymer of α-methyl styrene and Acrylonitrile Butadiene Stirene (AMS-ABS) and low density polyethylene (LDPE), of Composition by weight PVC / AMS-ABS / LDPE 100/60/10.

The compound from which it has been studied This mixture is a material marketed by the company AISCONDEL S.A. under the name of EF-0125. Said compound It consists of a polyvinyl chloride resin, synthesized in suspension and with Fikentscher constant value of K = 58, and various typical PVC additives, such as process modifiers, stabilizers, co-stabilizers and external lubricants. He AMS-ABS copolymer, marketed by GE Specialty Resins with the trade name BLENDEX 713, has a T_ {VICAT} B 120 / 49N of 114 ° C and a butadiene content of 14% in weigh. The LDPE used is a low density polyethylene commercialized by Repsol S.A. under the trade name ALCUDIA PE-017, which has a T_ {VICAT}, measured according to ASTM D-1525, 81 ° C and an index of fluidity, measured according to ASTM D-1238, of 7 g / 10 min.

Mixing has been carried out in two stages. First, a solid state premix has been carried out that it consists of a distributive manual dispersion, by means of a spatula, of the relevant amounts of each material in form of dust Subsequently, a state mixing has been carried out. cast in a mill of two Guix GX207 counter-rotating rollers. The premix is added to said mill at a temperature of T = 157 ° C and a mixing time of 4 minutes after the fusion, obtaining films that undergo a process of granceado by means of a die cutter The pellet obtained from these films has been used to prepare specimens suitable for mechanical tests and to feed the capillary extrusion rheometer. By pressing the  films under certain conditions of pressure, temperature and time, the corresponding specimens have been obtained to perform the mechanical, DMTA and T_ {VICAT} tests.

The mechanical properties have been compared (tensiometry and impact IZOD), the T_ {VICAT} and the properties rheology of: a) The PVC compound, called "PVC without mix ", corresponding to the commercial formulation of AISCONDEL, and b) the PVC / AMS-ABS / LDPE mixture, result of mixing the PVC compound with the other two cited polymers.

In order to study processability at deformation rates typical of industrial processing have been carried out continuous flow measurements in capillary extrusion at a temperature of 170 ° C, in the range of velocity gradients between 1 and 2.10 3 s -1. To bring about such measurements a capillary extrusion rheometer has been used Rheograph 2002 of the Góttfert house. It consists of a nozzle cylindrical, diameter 9.5 mm, where the thermostat is charged and material before forcing it to pass through a section capillary circulate by means of a piston driven by a hydraulic system. Be You have used a capillary of Length / Diameter ratio of L / D = 30, with a capillary radius of r_ {c} = 0.5 mm.

The flow curves obtained for PVC without mix and mix are shown in figure 1. It is noted that the mixture presents, in the range of gradients studied, a melt viscosity similar or lower than that presented by the PVC Thus, in the range of usual gradients for the processes of extrusion (in volume at 10 2 s -1), the mixture has a viscosity significantly lower than that presented by PVC, which represents a significant improvement in processability in said industrial process. On the other hand, in the range of gradients common for injection processes (in volume at 10 3 s -1), the mixture has a viscosity similar to that of PVC, so the processability in injection processes is barely going to see affected.

Table I shows the values of Vicat softening temperature (T_ {VICAT}), both with a load of 1 Kg. as with one of 5 Kg., tensile properties (tensile strain and tear strength) and values of left impact

TABLE I Values of T_ {VICAT} at 1 and 5 Kg. Properties Mechanical (Impact IZOD and tensiometry) of unmixed PVC and mix (PVC / AMS-ABS / LDPE)

one

Vicat softening temperature has been measure according to the UNE standard 53-118-78. The specimens for said test have a thickness of 3 mm and have been prepared in a GUMIX press model LP 25, at a temperature of 165ºC and pressure of 50 Kg / cm2, for 15 minutes. Then cool for 3 minutes The measurement of the T_ {VICAT} has been carried out in a thermostated bath with silicone oil, which leaves heating at a speed of 50 ° C / min.

On the other hand, traction measures have been carried out following the UNE standard 53-023-86. The test pieces for the test have a thickness of 1 mm and have been prepared in the press already described, at a temperature of 175 ° C with a pressure of 50 Kg / cm2 for 2 minutes and 180 Kg / cm2 for 3 minutes. Chilling later for 3 minutes. The tensile test has been performed on an INSTRON 4301 tensometer, at a speed of stretching of 10 mm / min., obtaining deformation values in tensile (%) and breaking strength (MPa).

The Izod impact resistance measures are have determined following the UNE standard 53-193-85. The test pieces for the test have a thickness of 3 mm and have been prepared in the press already described, at a temperature of 165 ° C and a pressure of 50 kg / cm 2 during 15 minutes.

The results, presented in table I, show that the mixture has temperature values of Vicat softening, with both 1 Kg and 5 Kg, very superior to those presented by PVC. This is an improvement of dimensional stability at high temperatures, which allows its use in areas of the market hitherto inaccessible to PVC On the other hand, tensile strain values and Breaking strength decrease, but they are still inside of the specifications of PVC consumers, which establish as minimum values 100% tensile strain and 32 MPa of breaking strength For its part, Izod impact resistance improves significantly.

Therefore, the mixture of the example presents, with respect to PVC, high dimensional stability improved temperatures and processability, without implying a significant worsening of other properties, such as tensile strength and deformation.

Example 2 Rheological and mechanical properties of a quaternary mixture PVC based

A quaternary mixture of a Polyvinylchloride compound (PVC), polymethyl methacrylate (PMMA), a PVC and acrylate graft copolymer (PVC-Acr) and low density polyethylene (LDPE), of Composition by weight PVC / PMMA / PVC-Acr / LDPE 100/50/15/10.

The compound from which it has been studied This mixture is a material marketed by the company AISCONDEL S.A. under the name of EF-0125. Said compound is It consists of a polyvinyl chloride resin, synthesized in suspension and with Fikentscher constant value of K = 58, and various typical PVC additives, such as process modifiers, stabilizers, co-stabilizers and external lubricants. PMMA employee is marketed by Degussa, belonging to Roehm GmbH and CoKG, under the trade name PLEXIGLAS 8N. The copolymer of PVC-Acr graft, marketed by Vinnolit house with the commercial name VINNOLIT K 704, it has a content in 50% acrylate. The LDPE used is a low polyethylene density sold by Repsol S.A. under the trade name ALCUDIA PE-017, which presents a T_ {VICAT}, measured according to ASTM D-1525, 81 ° C and a flow rate, measured according to ASTM D-1238, 7 g / 10 min.

The mixing method as well as the conditions for the study of processability (extrusion rheometry capillary), T_ {VICAT} and mechanical properties (Izod Impact and tensiometry) are the same as those described for example 1.

The flow curves obtained for PVC without mix and quaternary mixture are shown in figure 2. By On the other hand, table II shows the temperature values Vicat softening (T_ {VICAT}), both with a load of 1 Kg. As with one of 5 Kg., Tensile properties (deformation in tensile and tear strength) and Izod impact values.

TABLE II Values of T_ {VICAT} at 1 and 5 Kg. Properties Mechanical (Impact IZOD and tensiometry) of unmixed PVC and Mixing (PVC / PMMA / PVC-Acr / LDPE)

2

The results obtained in the different tests are similar to those obtained with the mixture of example 1, so the comments made in that example are equally valid for the current example.

Claims (17)

1. Polymeric mixture characterized in that it comprises

-

between 10 and 95% by weight of PVC based resin,

-

between 2.5 and 87.5% by weight of a compound capable of producing an increase in the T_ {VICAT} of PVC when mixed with it, and

-

between 2.5 and 70% by weight of a third component, which modifies the mechanical properties and / or viscosity.

2. Mixture according to claim 1, characterized in that the PVC-based resin is a resin obtained by a known polymerization process, selected from suspension, mass, solution, emulsion, dispersion and microsuspension processes. 3. Mixture according to any of claims 1 and 2, characterized in that the PVC-based resin is a vinyl chloride copolymer with a monomer selected from the group consisting of acrylic esters, methacrylic esters, monoolefins, diolefins, styrene derivatives, acrylonitrile, vinyl esters, vinylidene chloride, vinyl ethers and crosslinkable monomers such as allyl methacrylate and diallyl phthalate. 4. Mixture according to any of claims 1 and 2, characterized in that the PVC-based resin is a copolymer of vinyl chloride with a monomer selected from the group consisting of ethylene, propylene, 1-butene, 2-butene, 1-pentene, 1-hexene, isobutylene and vinylidene chloride. 5. Mixture according to any of the preceding claims, characterized in that the PVC has in its composition at least one additive selected from stabilizers, plasticizers, extenders, lubricants, fillers, pigments, process aids and impact modifiers. 6. Mixture according to any of the preceding claims, wherein the improved Vicat softening temperature (T_ {VICAT}) is a polymer or copolymer miscible or partially miscible with the PVC - based resin. 7. Mixture according to any of the preceding claims, characterized in that the compound capable of producing an increase in the T VICAT of PVC is an acrylic polymer or copolymer. 8. Mixture according to claim 7, characterized in that said acrylic-type polymer is selected from the group consisting of alpha-methyl styrene and acrylonitrile-butadiene-styrene copolymer (AMS-ABS), acrylonitrile-butadiene-styrene copolymer (ABS) and polymethyl methacrylate (PMMA). 9. Mixture according to any of the preceding claims, characterized in that the third component is one or more polymers, copolymers or mixture of both, capable of reducing melt viscosity and / or improving the mechanical properties of the mixture. 10. Mixture according to any of the preceding claims, characterized in that the third component is selected from linear and / or branched polyethylene, ethylene and vinyl acetate (EVA) copolymer, modified or unmodified, polycaprolactone, polylactone, polylaurillactone and copolymer in acrylate base. 11. Mixture according to claim 10, wherein the EVA copolymer comprises 10% to 80% by weight vinyl acetate and 90% to 20% by weight of ethylene. 12. Mixture according to claim 10, characterized in that the EVA copolymer is modified. 13. Mixture according to claim 12, characterized in that the EVA copolymer is modified with carbon monoxide (CO). 14. Mixture according to claim 10, characterized in that the acrylate-based copolymer is a PVC copolymer with polyacrylate. 15. Mixture according to claim 14, characterized in that the copolymer is graft, block, random or alternating. 16. Mixture according to any of the preceding claims, characterized in that it has a Vicat softening temperature measured according to UNE 53-118-78 higher than that presented by the PVC-based formulation.

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17. Mixture according to any of the preceding claims, characterized in that it has a melt viscosity equal to or less than that presented by PVC in the range of deformation rates between 1 and 2000 s -1.