GB1587259A - Stabilisers for synthetic resins - Google Patents

Description

(54) IMPROVEMENTS IN STABILISERS FOR SYNTHETIC RESINS (71) We, ASSOCIATED LEAD MANUFACTURERS LIMITED, of Clements House, 14-18 Gresham Street, London EC2V 7AT, a British Company, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: In the processing of vinyl resins it is necessary to incorpoate into the resin, stabiliser and lubricant ingredients. Otherwise an unacceptable product would be obtained due to the degradation and poor flow characteristics of the pure polymer.One method frequency used commercially to achieve stabilisation and lubrication of vinyl resins is to incorporate in the resin the following ingredients: (1) a stabiliser such as a basic lead salt of, for example, sulphuric, sulphurous, phosphorous, phthalic or carbonic acid, or mixtures thereof, (2) a lubricating stabiliser such as a metal soap of a long chain carboxylic acid which may typically contain 12 to 18 carbon atoms, for example lead stearate, basic lead stearate, calcium stearate or barium stearate, or mixtures thereof, and (3) a lubricant such as a natural or synthetic wax or mixtures thereof. Often other ingredients, such as plasticisers, for example dioctyl phthalate, or fillers will also be incorporated in the vinyl resin for other reasons.

A number of difficulties can arise from such factors as the handling of the stabiliser-lubricant ingredients, the dustiness of these ingredients, and the number of weighing operations necessary for the introduction of a number of ingredients into the complicated resin formulations frequently used. To overcome these difficulties a number of different products have been developed. Individual components have been offered in forms of reduced dustiness, for example flakes. Composite materials, containing the total stabiliser-lubricant mixture needed in any one individual situation, have also been presented in a single package. As a further extension these composite materials have been offered in forms of reduced dustiness. The main physical forms that have been marketed to date are either flakes or granules.The flaked product does not completely alleviate the problems of dustiness, although it is easy to handle in commercial processing equipment.

While granules can be produced in a substantially dustless form, they present difficulties in handling, primarily because they are normally of such size as to tend sometimes to cause blockages by bridging in handling equipment. Also granules which are large enough to be dustless are sometimes difficult to disperse with sufficient homogenity in the resin.

The present invention provides a method of producing a lubricating stabiliser additive, a wax lubricant additive, or a combined stabiliser and lubricant additive for incorporation in vinyl resins, which comprises discharging the additive in molten form through orifices as streams onto a conveyor which is travelling sufficiently fast for the emerging streams to deposit and solidify on the conveyor as continuous strands having a thickness in the range of 0.2 to 2.0 mm. and breaking the strands into pieces.

In use of this method a liquid is first obtained either by melting a lubricating stabilizer, a wax lubricant or a mixture of both or by preparing a dispersion of a pulverant stabiliser in a molten lubricating stabiliser, a wax lubricant or a mixture thereof, such dispersion optionally containing other additives for vinyl resins. The liquid so formed is then discharged through a series of orifices as molten streams onto a fast moving conveyor. It has been found that by moving the conveyor at a sufficiently high speed the emerging streams will deposit and solidify on the conveyor as continuous strands having a thickness in the range of 0.2 to 2.0 mm. preferably 0.25 to 0.75 mm. These strands are broken into pieces and the final product consists of fine straws which may be up to 4 cm. long, but preferably having a length of 0.1 to 1.0 cm.

The fine straws so obtained, unlike flaked materials, are substantially dustless. However, they are more readily dispersible in the resin than granules. The straws will normally contain all, or the majority of, the additives to be incorporated in the resin and include a basic lead salt, a metal soap and a wax lubricant. In particular cases, however, it may be convenient to produce straws consisting solely of the metal soap or of the wax lubricant.

The conveyor may be, for example, a belt, a disc or a drum. If the conveyor travels too slowly, the emerging streams of liquid form thick continuous strands, which both cool slowly and yield an unacceptable product. By running the conveyor at a sufficiently fast rate the streams are pulled out into thin strands of the above-specified thickness, which both cool rapidly due to the high ratio of surface area to volume and yield an acceptable product.

It has thus been found that these thin strands can be broken into straws with the formation of a minimal amount of very fine material, and thus give a substantially dustless final product. In the formation of flakes, for example, by breaking up sheets of solidified melt, it has proved impossible to limit the formation of very fine material and as a result the final product is significantly dusty.

An apparatus for use in carrying out the process is illustrated, by way of example, in the accompanying diagrammatic drawings, in which: Figure I shows the general layout of the apparatus; Figure 2 is a plan view of the tundish on a larger scale; and Figure 3 is a circuit diagram.

The apparatus shown in Figure 1 includes an electrically heated reservoir 10 in which the liquefiable constituents of the stabiliser/lubricant mixture are melted, a heated tundish 11 into which the melt from the reservoir is discharged intermittently under control of a solenoid-operated valve 12 and a stainless steel conveyor belt 13, disposed beneath the tundish and driven by an electric motor 14.

The reservoir 10 contains a stirrer 15 and the valve 12 is opened and closed under control of a timer 26 (Figure 3) so as to maintain a substantially constant head of liquid in the tundish 11. The melt flows in streams through orifices 16 in the base of the tundish onto the belt 13, on which it solidifies as strands which are collected in a container 17. The strands form coils in the container which can easily be broken into short lengths by hand tapping. If desired, however, the strands may be delivered by the belt to a screw conveyor which breaks them into short lengths.

As shown in Figure 3, the reservoir has a heating jacket 18, the temperature of which is controlled by a controller 19 connected to a thermocouple 20 in the reservoir. The tundish 11 also has a heating jacket 21, the temperature of which is controlled by a controller 22 connected to a thermocouple 23. The solenoid 24 controlling the valve 12 is constituted by a controller 25 which is under the joint control of an automatic timer 26 and a level sensor 27 in the tundish 11.

The belt may be provided with air or water cooling, e.g. by air jets directed against its upper surface or by water jets directed against the undersurface of its upper run.

Preferably the conditions of operation are as follows: Diameter of orifices 16 2 - 4 mm; Length of orifices 16 2 - 10 mm.

Temperature of melt in the reservoir 10 70 - 1500C.

Temperature of melt in the tundish 11 80 - 1600C.

Head of melt in the tundish 11 at least 5 mm.

Speed of belt 0.25 - 3 metres per sec., preferably 1 metre per sec.

The length of the belt may be 10 - 20 feet and a typical throughput per orifice can range from 0.5 - 3.0 kg/hr.

Typical formulations from which straw-like products with the above-mentioned properties have been prepared by the method of invention are set out in the following Table 1, in which parts are by weight. The following Table 2 sets out the operating conditions for test preparations on these typical formulations.

It was found that the straw-like samples from each of these test preparations were substantially dustless, possessed good dispersibility into vinyl resins and were eminently suitable to handling equipment typically used by commercial processors of vinyl resins. TABLE I Formulations used for experimental pilot plant runs Formulation number Components F1 F1(a) F2 F2(a) F2(b) F3 F4 F5 F6 F7 F7(a) Tetrabasic lead sulphate 24 - 54 - 54 74 79 84 - 74 Tribasic lead stearate - 24 - 54 - - - - - - 74 Dibasic lead stearate 10 15 10 10 10 - - - - 6 6 Calcium stearate 15 15 10 7 7 7 5 5 - 3 3 Normal lead stearate 40 40 18 18 18 15 10 10 100 10 10 Hard paraffin wax 3 3 3 3 3 5 - - - 3 3 Ester wax 7 7 7 7 7 - - - - 3 3 Soft paraffin wax - - - - - - 5 5 - - Carbon black - - - - 1 - - - - - Dioctyl Phthalate (Plasticiser) 1 1 1 1 1 1 1 1 - 1 7 TABLE 2 Operational details of the experimental pilot plant runs Run Number R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 Formulation Number F1 F2 F3 F4 F2(b) F6 F6 F1 F1(a) F2 F2(a) F7 F7(a) Melt Temperature ( C) 130 120 140 160 130 145 120 130 110 130 110 105 130 Tundish Temperature ( C) 130 120 160 145 130 170 130 130 120 130 115 105 130 Size of Tundish Orifices (mm.) 4.7 1.9 1.9 1.9 1.9 1.9 3.1 3.1 3.1 3.1 3.1 3.1 3.1 Head Height in Tundish (mm.) 30 80 30 40 80 40 50 90 90 80 90 50 90 Belt Speed (m/s) 0.25 0.25 0.25 0.25 0.25 0.24 2.5 2.2 2.5 1.7 1.8 2.5 2.5 Average Throughput per Orifice 1000 590 1000 1000 500 860 1550 1000 900 1700 1300 2000 3000 (g hr-1)

Claims (9)

WHAT WE CLAIM IS:

1. A method of producing a lubricating stabiliser additive, a wax lubricant additive, or a combined stabiliser and lubricant additive for incorporation in vinyl resins, which comprises discharging the additive in molten form through orifices as streams onto a conveyor which is travelling sufficiently fast for the emerging streams to deposit and solidify on the conveyor as continuous strands having a thickness in the range of 0.2 to 2.0 mm. and breaking the strands into pieces.

2. A method according to claim 1, wherein the thickness of the strands is 0.25 to 0.75 mm.

3. A method according to claim 1 or claim 2, wherein the strands are broken into fine straws having a length of up to 4 cm.

4. A method according to claim 3, wherein the length of the straws is 0.1 to 1.0 cm.

5. A method according to any one of the preceding claims, wherein the melt is a dispersion of a basic lead salt in a melt consisting of a metal soap and a wax lubricant.

6. A method according to any one of the preceding claims, wherein the conveyor is an endless belt.

7. A method according to any one of the preceding claims, wherein the melt is formed by melting constituents of the additive in a reservoir and is discharged from the reservoir into a tundish formed with the orifices through a valve which is controlled to maintain a substantially constant head of melt in the tundish.

8. A method according to claim 7, wherein the orifices have a diameter of 2 - 4 mm. and a length of 2 - 10 mm. the temperature of the melt in the reservoir is 70 - 1500C.,the temperature of the melt in the tundish is 80 - 1600C., the head of melt in the tundish is at least 5 mm. and the speed of the belt is 0.25 - 3 metres per second.

9. A method according to claim 1, substantially as described herein with reference to the accompanying drawings.