Transparent article made of PVC graft copolymers

Abstract

The invention relates to a method for preparing vinyl chloride graft copolymers by emulsion polymerization and to a method for preparing blends of such graft copolymers. The invention also relates to transparent molded articles prepared by using the graft copolymers according to the invention and their blends, respectively.

Claims

1. A vinyl chloride graft copolymer, comprising: a graft base having a first glass transition temperature; and a grafted copolymer phase having a second glass transition temperature and containing vinyl chloride, wherein the first glass transition temperature is lower than the second glass transition temperature, the graft base is not cross-linked and the grafted copolymer phase is cross-linked, the graft base is in an amount from 5 wt. % to 25 wt. % by weight of the vinyl chloride graft copolymer, and the grafted copolymer phase is in an amount from 75 wt. % to 95 wt. % by weight of the vinyl chloride graft copolymer.

2. The vinyl chloride graft copolymer of claim 1, wherein the first glass transition temperature is from about 80 C. to about 20 C. and the second glass transition temperature is from about 20 C. to about 120 C.

3. The vinyl chloride graft copolymer of claim 1, wherein the grafted copolymer phase includes from about 60 wt. % to about 100 wt. % vinyl chloride by weight of the grafted copolymer phase and from about 0 wt. % to about 40 wt. % by weight of the grafted copolymer phase other vinyl compounds.

4. A vinyl chloride graft copolymer comprising: a graft base prepared by polymerizing monomers, the graft base having a first glass transition temperature; a copolymer phase grafted onto the graft base by emulsion polymerization to obtain a vinyl chloride graft copolymer latex, the grafted copolymer phase having a second glass transition temperature wherein the first glass transition temperature is lower than the second glass transition temperature, the vinyl chloride graft copolymer separated as a solid from the vinyl chloride graft copolymer latex, wherein the graft base is not cross-linked and the grafted copolymer phase is cross-linked, the graft base is in an amount from 5 wt. % to 25 wt. % by weight of the vinyl chloride graft copolymer, and the copolymer phase is in an amount from 75 wt. % to 95 wt. % by weight of the vinyl chloride graft copolymer.

5. The vinyl chloride graft copolymer of claim 4, wherein the first glass transition temperature is from about 80 C. to about 20 C.

6. The vinyl chloride graft copolymer of claim 5, wherein the second glass transition temperature is from about 20 C. to about 120 C.

7. The vinyl chloride graft copolymer of claim 4, wherein the grafted copolymer phase includes about 60 wt. % to about 100 wt. % vinyl chloride by weight of the grafted copolymer phase and from about 0 wt. % to about 40 wt. % by weight of the grafted copolymer phase other vinyl compounds.

8. The vinyl chloride graft copolymer of claim 4, wherein the vinyl chloride graft copolymer has a transmittance of at least 65% as measured according to ISO 13468 for a plate having a thickness from 1.35 mm to 1.68 mm.

9. A method of forming a vinyl chloride graft copolymer, the method comprising: preparing a graft base by polymerizing monomers, the graft base having a first glass transition temperature; grafting a copolymer phase onto the graft base by emulsion polymerization to obtain a vinyl chloride graft copolymer latex, the grafted copolymer phase having a second glass transition temperature wherein the first glass transition temperature is lower than the second glass transition temperature; and separating the vinyl chloride graft copolymer as a solid from the vinyl chloride graft copolymer latex, wherein the graft base is not cross-linked and the grafted copolymer phase is cross-linked, the graft base is in an amount from 5 wt. % to 25 wt. % by weight of the vinyl chloride graft copolymer, and the grafted copolymer is in an amount from 75 wt. % to 95 wt. % by weight of the vinyl chloride graft copolymer.

10. The method of claim 9, wherein the first glass transition temperature is from about 80 C. to about 20 C.

11. The method of claim 10, wherein the second glass transition temperature is from about 20 C. to about 120 C.

12. The method of claim 9, wherein the grafted copolymer phase includes about 60 wt. % to about 100 wt. % vinyl chloride by weight of the grafted copolymer phase and from about 0 wt. % to about 40 wt. % by weight of the grafted copolymer phase other vinyl compounds.

Description

EXAMPLES

Example 1

(1) Graft Base:

(2) Into a 10-liter stirrer reactor with a water-cooled double jacket and equipped with a paddle agitator, 1166 g of deionized water, 68.6 g of butyl acrylate, 3088 g of a 1% solution of potassium myristate and 0.63 g of potassium peroxodisulfate were pre-charged and heated to 80 C. After the reaction had started, addition of 686 g of a 0.3% aqueous potassium peroxodisulfate solution within 180 min was started. Simultaneously, 1990 g of butyl acrylate were added within 180 min. After the addition had ended, the interior reactor temperature was maintained for 60 min and the preparation was cooled down subsequently. 6894 g of dispersion were discharged, having a solid content of 30 wt %, a surface tension of 51.6 mN/m and a pH of 7.6. The average volume-based particle size (PSV) was 12 nm.

(3) Graft Copolymer:

(4) Into a 10-liter autoclave with a water-cooled double jacket and a paddle agitator, 124 g of water, 1937 g of a 1% solution of potassium myristate, 3500 g of graft base and 1283 g of vinyl chloride were pre-charged and heated to 68 C. When the polymerization temperature was reached, addition of potassium peroxodisulfate and ascorbic acid was started. The adding speed was adjusted in such a way that the difference between the interior temperature and the supply temperature of the jacket cooling was about 10 C. After the pressure had dropped by 4 bar, the preparation was set to cool and depressurized. The dispersion was discharged. The solid content of the dispersion was 31.3 wt %, the surface tension was 56.6 mN/m, the pH was 8.3. The average volume-based particle size was 68 nm. The preparation was precipitated with calcium chloride and filtered by suction filtration. The residue was dried at 30 C. in a recirculating-air dryer to a residual moisture of <0.3% and finely ground with a centrifugal mill (Retsch ZM 200). The PBA content was determined to be 48.6 wt % by an oxygen analysis.

Example 2

(5) Graft Base:

(6) The graft base was prepared following Example 1. 6936 g of dispersion were discharged, having a solid content of 30 wt %, a surface tension of 49 mN/m and a pH of 7.5. The average volume-based particle size was 14 nm.

(7) Graft Copolymer:

(8) 407 g of water, 2471 g of a 1% potassium myristate solution, 2330 g of graft base and 1633 g of vinyl chloride were pre-charged and polymerized following Example 1. The dispersion was discharged. The solid content of the dispersion was 30.1%, the surface tension was 57.8 mN/m, the pH was 8.8. The average volume-based particle size was 64 nm. The preparation was precipitated with calcium chloride and filtered by suction filtration. The residue was dried at 30 C. in a recirculating-air dryer to a residual moisture of <0.3% and finely ground with a centrifugal mill (Retsch ZM 200). The PBA content was determined to be 34.4 wt % by an oxygen analysis.

Example 3

(9) Graft Base:

(10) The graft base of Example 2 was used.

(11) Graft Copolymer:

(12) 894 g of water, 2800 g of a 1% potassium myristate solution, 1167 g of graft base and 1983 g of vinyl chloride were pre-charged and polymerized following Example 1. The dispersion was discharged. The solid content of the dispersion was 29.7%, the surface tension was 59.1 mN/m, the pH was 9.0. The average volume-based particle size was 46 nm. The preparation was precipitated with calcium chloride and filtered by suction filtration. The residue was dried at 30 C. in a recirculating-air dryer to a residual moisture of <0.3% and finely ground with a centrifugal mill (Retsch ZM 200). The PBA content was determined to be 26.6 wt % by an oxygen analysis.

Example 4

(13) Graft Base:

(14) Into a 10-liter stirrer reactor with a water-cooled double jacket and equipped with a paddle agitator, 1791 of deionized water, 68.6 g of butyl acrylate, 0.63 g of potassium peroxodisulfate and 61.76 g of a 1% solution of potassium myristate were pre-charged and heated to 80 C. After the reaction had started, 1029 g of a 0.2% aqueous solution of potassium peroxodisulfate, 1990 g of butyl acrylate and 2059 g of a 1% potassium myristate solution were added within 180 min. After the addition had ended, the interior reactor temperature was maintained for 60 min and the preparation was cooled down subsequently. 6964 g of an aqueous dispersion having a solid content of 29.4 wt %, a surface tension of 50.1 mN/m and a pH of 8.1 were obtained. The average volume-based particle size was 227 nm.

(15) Graft Copolymer:

(16) Into a 10-liter autoclave with a water-cooled double jacket and a paddle agitator, 1863 g of water, 482 g of a 1% solution of potassium myristate and 3280 g of graft base were pre-charged and heated to 68 C. Subsequently, 120.6 g of vinyl chloride were added at once and further 1326 g of vinyl chloride were added within 100 min. For the activation, hydrogen peroxide and ascorbic acid solutions were used, the adding speed of which was regulated in such a way that the difference between the interior temperature and the supply temperature of the jacket cooling was about 10 C. After the pressure had dropped by 4 bar, the preparation was set to cool and depressurized. The dispersion was discharged. The solid content of the dispersion was 30.2 wt %, the surface tension was 53 mN/m, the pH was 7.3. The average volume-based particle size was 301 nm. The preparation was precipitated with calcium chloride and filtered by suction filtration. The residue was dried at 30 C. in a recirculating-air dryer to a residual moisture of <0.3% and finely ground with a centrifugal mill (Retsch ZM 200). The PBA content was determined to be 46.6 wt % by an oxygen analysis.

Example 5

(17) Graft Base:

(18) Into a 10-liter stirrer reactor, 3637 g of deionized water, 68.64 g of butyl acrylate, 617.6 g of potassium myristate (concentration: 5 wt %) and 0.63 g of potassium peroxodisulfate were pre-charged and heated to 80 C. After the reaction had started, addition of 686 g of a 0.3% aqueous solution of potassium peroxodisulfate within 180 min was started. Simultaneously, 1990 g of butyl acrylate were added within 180 min. After the addition had ended, the interior reactor temperature was maintained for 60 min and the preparation was cooled down subsequently. 6947 g of an aqueous dispersion having a solid content of 29.9 wt %, a surface tension of 50.3 mN/m and a pH of 7.5 were obtained. The average volume-based particle size was 23 nm.

(19) Graft Copolymer:

(20) 1064 g of water, 332 g of a 5% potassium myristate solution, 3144 g of graft base, 1052 g of vinyl chloride and 8.0 g of diallyl phthalate were pre-charged and polymerized following Example 1. The solid content of the dispersion was 30.3 wt %, the surface tension was 55.6 mN/m, the pH was 7.6. The average volume-based particle size was 102 nm. The preparation was precipitated with calcium chloride and filtered by suction filtration. The residue was dried at 30 C. in a recirculating-air dryer to a residual moisture of <0.3% and finely ground with a centrifugal mill (Retsch ZM 200). The PBA content was determined to be 50 wt % by an oxygen analysis.

Example 6

(21) Graft Base:

(22) Into a 10-liter stirrer reactor, 1791 g of deionized water, 68.64 g of butyl acrylate, 61.76 g of potassium myristate (concentration: 1 wt %) and 0.63 g of potassium peroxodisulfate were pre-charged and heated to 80 C. After the reaction had started, addition of 1029 g of a 0.2% aqueous solution of potassium peroxodisulfate within 180 min was started. Simultaneously, 1990 g of butyl acrylate and 2059 g of a 1% aqueous solution of potassium myristate were added within 180 min. After the addition had ended, the interior reactor temperature was maintained for 60 min and the preparation was cooled down subsequently. 6824 g of an aqueous dispersion having a solid content of 29.5 wt %, a surface tension of 47.1 mN/m and a pH of 8.4 were obtained. The average volume-based particle size was 274 nm.

(23) Graft Copolymer:

(24) The preparation was prepared following Example 5. The solid content of the dispersion was 27.2 wt %, the surface tension was 42.1 mN/m, the pH was 8.5. The average volume-based particle size was 321 nm. The preparation was precipitated with calcium chloride and filtered by suction filtration. The residue was dried at 30 C. in a recirculating-air dryer to a residual moisture of <0.3% and finely ground with a centrifugal mill (Retsch ZM 200). The PBA content was determined to be 55.7 wt % by an oxygen analysis.

(25) Experimental Procedures:

(26) Measurement of Particle Sizes:

(27) The particle size distributions were measured with a Microtrac Blue-Wave of the S 3500 series by Particle Metrix. The valid measuring range lies between 0.01 and 2000 m. For the measurement, a standard procedure for dispersions was created, where certain physical properties of the dispersion were given. Before measurement, three drops of Hellmanex by Hellma Analytics Co. were added to the deionized water inside the circulation unit, using a disposable 3 ml pipette. The cleanliness of the measurement system was validated by a baseline measurement. Dispersion was added carefully to the sample unit until a loading factor of about 0.004 was reached. Normally, 1 or 2 drops of dispersion are used. The measurement time was 30 s. Evaluation of the measurement is carried out automatically. The average volume-based particle size is used.

(28) Two-Roll Rolling Mill (Including Processing Conditions and Recipe)

(29) In order to determine mechanical values and optical properties, test samples have to be provided. The preparation of the rolled sheets is performed under the following conditions.

(30) Recipe (Spatula Blend)

(31) TABLE-US-00001 100 phr Polymer 1.5 phr BaZn stabilizer (Baerostab UBZ 171) 3.0 phr Epoxydated soy bean oil (Edenol D 81) 0.1 phr Isotridecyl stearate (Loxiol G 40) 0.2 phr High-molecular weight multicomponent ester (Loxiol G 72) 0.1 phr Calcium stearate (Ceasit SW)

(32) Rolling mill (made by Schwabenthan)

(33) Roller material: chromed surfaces

(34) Roller diameter: 150 mm

(35) Speed ratio: 17/21 1/min

(36) Roller temperature: 140 C.

(37) Rolling time: 5 min

(38) Execution:

(39) In order to form a cohesive mass (sheet), the powder compound is placed onto the roller. After formation of the sheet, the sheet is cut and turned for 3 min. Then set the thickness of the rolled sheet to 1.1 mm and continue to plasticize the sheet on the roller for further 2 min without cutting and turning. When the specified rolling time is over, the rolled sheet is taken off.

(40) Press

(41) 30-ton laboratory press (Werner & Pfleiderer URH 30)

(42) Press area: 350350 mm

(43) Pressing plates: chromed surfaces

(44) Pressing frame: 2202201.0 mm

(45) Execution:

(46) For making the press plates, the previously produced rolled sheets were cut corresponding to the frame size used, inserted into the frame and placed into the laboratory press together with the press plates that form the outer surfaces. The sheets are formed into a press plate under the conditions described below.

(47) TABLE-US-00002 Press temperature: 150 C. LP press power: 30 bar LP pressing time: 2 min HP press power: 200 bar HP pressing time: 3 min Removal temperature: 40 C. Cooling pressure: 200 bar Cooling time: ca. 8 min
Transmittance and Haze (Large-Angle Scattering)

(48) In order to evaluate a film's transparency, two values were considered: the total transmittance (here: transmittance), which stands for the ratio of transmitted light to incident light and which depends on absorption properties and surface conditions large-angle scattering (haze), which is a measure for opaqueness.
Measurement:

(49) Measurement of the transmittance and determination of the large-angle scattering of the semi-finished products produced with rollers/presses is carried out with the transparency meter Haze-Gard Dual by Byk-Gardner Inc.

(50) The sample to be measured is illuminated perpendicularly and the transmitted light is photoelectrically measured in an integrating sphere. In this process, the perpendicularly transmitted light is measured in order to evaluate the transmittance, and the light that is scattered in an angle of 2 to the axis of irradiation is measured to evaluate the opaqueness (haze). The measurements are carried out according to ISO 13468, which guarantees that the measurement conditions are the same during calibration as well as during measurement.

(51) TABLE-US-00003 TABLE 1 Overview: Test- and Comparative Examples and Press Plates Made Therefrom Thickness of PBA content Microtrac MV Press Plates Patent Examples (wt %) (nm) Shore Hardness A Shore Hardness D (mm) Transmittance, % Haze Remarks Example 1 48.6 68 88 28 1.46 84.7 11.2 Graft base and Example 2 34.4 64 53 1.46 77.2 36.5 graft shell non- Example 3 26.6 46 64 1.63 72.2 26.8 cross-linked Example 4 46.6 301 39 1.35 83.3 7.65 Example 5 50 102 84 29 1.60 85.3 11.7 Graft base non- Example 6 55.7 321 52 10 1.68 69.5 26.5 cross-linked and graft shell cross- linked Blend Example 1 41.5 41 1.56 78.4 24.4 0.50 Example 1 + 0.50 Example 2 Vinnolit VK ca. 50 85 28 1.48 78.0 65.8 Competitive 710 product samples Vinnolit K ca. 50 79 25 1.81 53.9 68.8 707 E

(52) The graft copolymers Vinnolit VK 710 and Vinnolit K 707 E, having a content of about 50 wt % of acrylate, represent the prior art. Particularly due to the high haze value (which characterizes the large-angle scattering), the press plates appear translucent to opaque. The examples according to the invention have a much better transparency, which in particular is characterized by a substantially lower light scattering. The test- and comparative examples give prove of the effect of the cross-linking of the graft base of the graft copolymers on the transparency of PVC articles manufactured therefrom.