NO146674B - INTERNAL PLASTIFIED COPOLYMER - Google Patents

Description

The present invention relates to an inner plasticized vinyl chloride copolymer which can be used in such applications where outer plasticized polyvinyl chloride is used, e.g. as a vinyl film or vinyl sheet material, in vinyl wire and vinyl cable insulation, as vinyl floor coverings and as bags and tubes in blood transfusion equipment.

Externally plasticized vinyl chloride polymers are well known. It is characteristic that these products contain certain amounts of external plasticizers to give the polymers the desired degree of flexibility. However, the technique of external plasticization is not completely satisfactory since the plasticizers tend to migrate to the surfaces of the final product and cause such problems as surface tackiness, gradual loss of plasticity, and danger of possible toxicological damage to the consumer from the plasticizer. The aromatic plasticizers used in such products also cause a lot of smoke formation when the products are burned, and bending at fairly high temperatures requires the input of quite a lot of energy during processing.

A number of methods have previously been proposed for the formation of internally plasticized vinyl chloride copolymers. Use of copolymers of a vinyl monomer and a polymerizable polyester, e.g. an acrylate or vinyl ester of a polyester of an aliphatic hydroxycarboxylic acid, was proposed in U.S. Patent No. 3,640,927. An internally plasticized two-component vinyl chloride copolymer containing from approx. 75 to approx. 95% vinyl chloride and approx. 25 to approx.

5% of an ester of an unsaturated mono- or polycarboxylic acid, e.g. a <C>g<->C^2~a-'-'cYlmaleate< -fumarate or -acrylate, was proposed in U.S. Patent No. 3,544,661. The present invention relates to a composition which contains at least three basic components. Finally, a polymer composition with four components containing vinyl chloride, a dialkyl maleate or fumarate, an alkyl ester of

acrylic or methacrylic acid and a monohydrogen, monoalkyl maleate or fumarate, proposed in U.S. Patent No. 3,196,133, for use as a solvent-based coating with both good adhesion and flexibility. According to U.S. Patent No. 3,196,133, a low molecular weight C 1 -C 2 -dialkyl maleate or -fumarate is used as a component, while according to the present invention, C 8 -C 22 -d 3 -alkyl maleate °g -fumarates are used.

A plasticized polyvinyl chloride composition must be flexible at low temperature and have physical toughness to be commercially useful. The flexibility at low temperature can be measured by the well-known Clash-Berg method, with a value of -25°C or lower being preferred. Physical toughness can be determined by measuring the tensile strength at break, as a value of approx. 84 kg/cm<2 >or higher. There are standard ASTM tests for both of the above provisions, e.g. respectively ASTM D1043 and ASTM D638-72.

There is a theory that conventional external plasticization partially reduces the crystallinity of the vinyl chloride polymer, thereby achieving better flexibility at low temperature while leaving sufficient crystallinity to not reduce the physical toughness of the polymer. Internally plasticized vinyl chloride copolymers, on the other hand, often have a reduced crystallinity for the polymer, and this can essentially be zero if a large enough amount of plasticizing comonomers is used. It was proposed by R. Liepins in "Polymer Engineering and Science",

volume 9, no. 2 (March 1969), pp. 86-89 that a possible solution to this problem is the use of high molecular plasticizing comonomers so that the mole fraction of such comonomers is low while their weight percentage is high. Although comonomers such as C 8 -C 22 ""t-alkyl rumarates and maleates satisfy this description, their use together with vinyl chloride monomer does not provide a vinyl chloride copolymer having the desired flexibility at low temperature and excellent physical properties, e.g. good tensile strength. As will be shown in the following examples, the use of such comonomers as the high molecular weight dialkyl fumarates and maleates, or for that matter the high molecular weight alkyl acrylates, will produce a product which has the desired flexibility at low temperature but which also has other physical properties which is not suitable for the intended product, e.g. unacceptably low tensile strength.

It has unexpectedly been found that an internally plasticized vinyl chloride polymer having a Clash-Berg value of approx. -20°C or lower, preferably -25°C or lower, and a tensile strength at break of at least 59.5 kg/cm 2 or higher, preferably 84 kg/cm 2 or higher, can be formed by conventional emulsion, suspension, bulk and solution polymerization processes using a monomer charge with three basic components containing a certain amount of vinyl chloride, a C2-C20 alkyl acrylate and a C8-C22-' ^or~ stepwise a cn~ C22~' dial-kylmaleate or -fumarate. The invention is an internal plasticized copolymer consisting of from 45 to 80% by weight of vinyl chloride, from 15 to 54% by weight of a C2-C10 alkyl acrylate and from 1 to 15% by weight of a C8-C22 dialkyl maleate or fumarate, these monomers are polymerized together. If desired, mixtures of the respective alkyl acrylates and of the dialkyl maleates or fumarates can be used. A preferred copolymer is a terpolymer formed by the copolymerization of from 60 to 75% by weight of vinyl chloride, from 20 to 35% by weight of a C2-C10 alkyl acrylate and from 4 to 15% by weight of a C8-C22 dialkyl maleate or fumarate .

Representative C 1 -C 1 -alkyl acrylates which can be used in the practice of the present invention include ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, t-butyl acrylate, n- and other isomeric pentyl acrylates, n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate and mixtures of the aforementioned acrylates.

The C8-C22-dialkyl maleates and fumarates which are suitable for use in the present invention can, if desired, be formed by reacting a mixture of C8-C4-aliphatic alcohols, e.g. a mixture of C 2 -C 22 alcohols, which are commercially available as "Conoco LTD" alcohol from Continental Oil Co., with either maleic anhydride or fumaric acid, such as e.g. indicated in Example 1 below. Alternatively, individual C8-C22 dialkyl maleates or fumarates can be used. Representative maleates and fumarates that may be used include di-2-ethylhexyl maleate and fumarate, diundecyl maleate and fumarate, didodecyl maleate and fumarate, ditridecyl maleate and fumarate, dioctadecyl maleate and fumarate and didocosamaleate and fumarate and mixtures thereof. The mixed maleates or fumarates can be prepared by mixing the individually prepared di-alkyl esters or by mixing the alcohols together and then carrying out the esterification reaction.

The copolymer according to the present invention can be formed by conventional mass, emulsion, suspension and solution polymerization processes. Suspension polymerization is preferred because it avoids the problems of isolating the product from a latex encountered when using emulsion polymerization techniques, the heat of reaction is removed more easily than in mass polymerization processes, and no solvent recovery is necessary, such as by solution polymerization.

Reaction mixtures in suspension polymerization comprise from 20 to 45% by weight, based on the amount of water, of the monomers listed above in an aqueous reaction medium. There will also be included from 0.05 to 5% by weight, based on the weight of the monomers, of a suspending agent, e.g. methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, gelatin and the likej and from 0.005 to 1% by weight, based on the monomer amount, of at least one monomer-soluble initiator, e.g. azobisiso-butyronitrile, lauroyl peroxide, benzoyl peroxide or isopropyl peroxide dicarbonate. The polymerization is carried out by heating the suspension containing the above-mentioned components to a temperature of from 35 to 75°C for 2 to 12 hours, stirring throughout the reaction. As is well known in the industry, the use of the most active of the above-mentioned initiators will require the use of either a lower temperature or a shorter reaction time, or both, while the use of the less active initiators will not require stricter conditions.

If emulsion polymerization is used, the suspending agent described above is replaced with from 0.2 to

2% by weight of an emulsifier, e.g. sodium lauryl sulfate, potassium stearate, an alkyl benzene sulfonate, an ammonium dialkyl sulfosuccinate, and the like, and the monomer-soluble initiator is replaced by from 0.1 to 1% of a water-soluble initiator, e.g. an alkali metal persulfate, perborate or peracetate, ammonium persulfate perborate or peracetate, urea peroxides, hydrogen peroxide, tertiary butyl hydroxyperoxide and the like. If desired, a redox initiator system can be used as initiator, e.g. ammonium persulphate and sodium bisulphite or hydrogen peroxide and ascorbic acid. The polymerization is carried out at similar temperatures and similar time periods to those used in suspension

tion polymerization.

If mass polymerization is used, the monomers are polymerized in the presence of the above-described amounts of monomer-soluble catalysts alone under the same temperature and time conditions as described above in connection with suspension and emulsion polymerization.

If solution polymerization is used, the monomers are polymerized in the presence of at least one inert organic solvent, e.g. butane, pentane, octane, benzene, toluene, cyclohexane, cyclohexanone, acetone, isopropanol, tetrahydrofuran and the like . The chosen initiator should be soluble in the reaction medium. The copolymer can either remain dissolved in the solvent at the end of the polymerization or it can precipitate from the liquid phase during the polymerization. In the former case, the product can be recovered by evaporation of the solvent or by precipitation precipitation of the polymer solution by combining it with a non-•solvent for the product.The same reaction conditions as used in suspension and emulsion polymerization can be used.

The final product according to the present invention can, if desired, contain various possible additives which are compatible with the copolymer product and which have no detrimental effect on the properties of said product. Included in this group of additives are "such light stabilizers, ultraviolet stabilizers, pigments, fillers, dyes and other additives as are known to the person skilled in the art. A suitable list of possible additives that the person skilled in the art can use to select the appropriate additives, are given in the Modern plastics Encyclopedia, vol. 51, no. 10A, eg on pages 735-754.

The following examples illustrate certain preferred embodiments of the present invention:

Example 1

This example illustrates a method for producing an alkyl ester of fumaric acid which is suitable for use in producing the copolymer composition according to the invention.

The ractants listed in the table below were placed in a round-bottom flask of 3 litres, equipped with a Dean & Stark trap, condenser, stirrer, thermometer and nitrogen intake:

The reactants were heated and stirred at a temperature of 110-160°C for approx. 3-5 hours, and 50 ml of water was removed as azeotrope. The reactants were then heated together with nitrogen purging at a temperature of from 180 to 220°C to remove the naphtha. The oily product obtained was washed with a 5% by weight solution of sodium hydroxide followed by washing with water until the water was neutral when tested with litmus paper. the yield was 836 g or 96% of theoretical, and the product had a molecular weight of 570. This product was designated "product A".

Example 2

This example illustrates a method for producing a vinyl chloride/fumarate ester/acrylate terpolymer in accordance with the present invention. The fumarate ester was prepared by the same method as stated in example 1.

The reactants listed in the table below were placed in a one-quart soda bottle which was then frozen at -15°C for 2 hours:

To this cooled bottle was then added 2.5 ml of a 10% by weight solution of isopropyl peroxydicarbonate initiator in heptane and 65 g of vinyl chloride monomer. The bottle was covered and clamped in a bottle polymerization apparatus which was then rotated at 35 revolutions per minute. minute under heating at 45°C for 12 hours. After cooling to room temperature, the bottle was vented and no unreacted vinyl chloride monomer was detected. The product, a white suspension slurry, was filtered through a Buchner funnel and dried.

Using a similar method, a number of other tests were also carried out, and also together with other copolymer compositions for comparison. Table 1 shows the results:

Example 3

100 grams of each of the samples listed in Table 1 in Example 2 were mixed with the following ingredients:

Each of the samples was processed on a two-roll mill at 132.2-148.9°C for 7-10 minutes and was press-molded and die-cut. Each of them was then tested by a series of ASTM methods. The results are shown in table 2:

The outer plasticized PVC (Sample 9) showed good flexibility at low temperature, as measured by its Clash-Berg reading, and good tensile properties. The vinyl chloride/Cg-fumarate copolymer (Sample 3) showed a lack of both low temperature flexibility and elasticity, the vinyl chloride/C^2-C22~^umarate-^°P°^^mer (Sample ^) had excellent low temperature flexibility but very poor tensile strength and the vinyl chloride/acrylate copolymer (Sample 2) was somewhat deficient in low temperature flexibility and % elongation at break. Sample 5, which contains 10% or more of a fumarate ester, has excellent flexibility at low temperature if one can tolerate a reduction of the tensile strength at break to approx. 59.5 to 63 kg/cm 2 . Samples 1, 6 and 8, which are the preferred compositions of this invention, had a Clash-Berg value of -31.1°C or less, a tensile strength at break of 84 kg/cm 2 or higher and a % elongation in the event of a breach of o at least 230% or higher. Commercially useful flexible vinyl products can be made using these resin compositions which contain no migrating plasticizers. These products will avoid the aforementioned problems usually associated with plasticizer migration from outer plasticized PVC films.

The product according to this invention is therefore an internally plasticized composition which does not have surface tackiness, gradual loss of plasticity, danger of possible toxicological damage to the consumer from the plasticizer and abundant smoke formation when the product is burned, which is characteristic of certain externally plasticized products which previously known in the industry. Moreover, the products according to the present invention are pliable at lower temperatures than conventionally plasticized products, and therefore a smaller energy input is needed for such manufacturing techniques as painting and the like.

In the foregoing, certain preferred embodiments of the invention are illustrated. The extent of the protection sought is stated in the following requirements.

Claims (4)

1. Inner plasticized copolymer, e.g. for use in film or sheet material, in wire and cable insulation or in floor coverings, characterized in that it consists of: (1) 45-80% by weight vinyl chloride; (2) 15-54% by weight of a <C>2<->Cl0 alkyl acrylate; and (3) 1-15% by weight of a <C>g<->C22 dialkyl maleate or fumarate, or mixtures thereof. 2. Copolymer according to claim 1, characterized in that it consists of 60-75% by weight vinyl chloride, 20-35% by weight C2-C10 alkyl acrylate and 4-15% by weight C8-C22 dialkyl maleate or fumarate or mixtures thereof. 3. Copolymer according to claims 1 and 2, characterized in that component (2) is 2-ethylhexyl acrylate. 4. Copolymer according to claim 1, characterized in that component (3) is a mixture of <^ i2~(~ 22~ dialkyl fumarates.