GB2107719A - Hindered piperidine stabilizers for synthetic resins - Google Patents

Abstract

It has been found that, by blending a specific hindered piperidine compound with synthetic resins, composition having very good light-stability are produced. Such stabilized compositions consist of a synthetic resin blended with a piperidine compound of the following general formula: <IMAGE> wherein R represents a hydrogen atom or a methyl radical.o

Description

SPECIFICATION Stabilized synthetic resin composition The present invention relates to synthetic resin compositions having an excellent stability against light.

It is well known that synthetic resins such as polethylene, polypropylene, polyvinyl chloride, polyurethane, ABS resin, etc. are deteriorated by the action of light and are remarkably lowered in their physical properties, accompanied with phenomena such as softening, embrittlement, discoloration etc. To prevent such deterioration by light, various kinds of light stabilizers have been heretofore added during the steps of production and molding of synthetic resins.

As such light stabilizers, there are known for example 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4octoxybenzophenone, 2(2-hydroxy-5-methyl phenyl) benzotriazole, 2(2-hydroxy-3-t-butyl-5-methyl phenyl)-5- chlorobenzotriazole, 2(2-hydroxy-3,5-dipenthylphenyl)benzotriazole, ethyl-2-cyano.3,3-diphenyl acrylate, 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate, [2,2'-thiobis(4-t-octylphenolate) An-butylamine nickel (II), bis(3,5-di-t-butyl-4-hydroxybenzyl phosphoric acid)monoethyl ester Ni-salt, bis(2,2,6,6-tetramethyl-4piperidyl) sebacate, etc.Among these light stabilizers, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, which is a compound of hindered piperidines, is particularly excellent in respect of resistance to light, but there has been a problem in its susceptibility to hydrolysis in practical use.

We studied intensively to solve this problem, and as a result, we have found that, by blending a specific hindered piperidine compound with synthetic resins, a very good resistance to light can be obtained in comparison with the case of using the conventional light stabilizers. This discovery led us to the present invention.

The present invention provides a stabilized synthetic resin composition characterized by a synthetic resin blended with a piperidine compound of the following general formula (I):

wherein R represents a hydrogen atom or a methyl radical.

As such hindered piperidine compounds of the formula (I), there can be mentioned as concrete examples bis(2,2,6,6-tetra methyl-4-piperidyl)thiou rea and bis( 1 ,2,2,6,6-pentamethyl-4-piperidyl)thiourea.

Such compounds of the general formula (I) can be produced by heating, in the presence of iodine, 2,2,6,6-tetramethyl-4-piperidyidithiocarbamic acid shown by the following general formula (ill):

wherein R has the same meaning as the formula (I).

In the synthetic resin compositions of the present invention the blending amount of the hindered piperidine compound (I) is generally 0.01 to 5 weight parts, preferably 0.05 to 2 weight parts, for 100 parts of the synthetic resin.

In order to blend the piperidine compound with synthetic resins, any known apparatus and methods for blending stabilizers, pigments, fillers, etc. with synthetic resins can be employed without substantial modification.

The synthetic resin composition of the present invention may contain, if necessary, other additives for example antioxidants, light stabilizers, metal deactivating agents, metallic soaps, nucleating agents, lubricants antistatic agents, flame retardants, pigments and fillers.

Especially, by the addition of phenolic antioxidants, it is possible to improve stability against heat and oxidation. As such phenolic antioxidants, there can be mentioned for example 2,6-di-t-butyl-4-methylphenol, n-octadecyl-ss-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 1,1 ,3-tris(2-methyl-4-hydroxy-5-t- butyl phenyl)butane,l ,3,5-tri m ethyl-2,4,6-tris(3,5-di-t-butyl-4-hyd roxybenzyl) benzene, 1 ,3,5-tris(3,5-di-t butyl-4-hydroxybenzyl) isocyan u late,1,3,5-tris [p-(3,5-di-t-buWl-4-hydroxyphenyl)propionyloxyethylj- isocyan u late, 1 ,3,5-tris (2,6-di-methyl-3-hydroxy-4-t-butylbenzyl)isocyanulate, pentaerythritol-tetrakis [p- (3,5-di-t-butyl-4-hydroxyphenyl) propionate,] etc.

Furthermore, by the addition of a phosphite type antioxidant to the synthetic resin composition of the present invention, it is possible to improve its color. As such phosphite type antioxidants there can be mentioned for example, tris(nonylphenyl)phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tbutylphenyl)phosphite, tris(2-t-butyl-4-methylphenyl)phosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, tetrakis(2,4-di-t-butylphenyl)4,4'-biphenylene diphosphite etc.

It is also possible to add a sulfur containing antioxidant to the synthetic resin composition of the present invention. As such sulfur containing antioxidants there can be mentioned for example, dilauryl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, pentaerythritol tetrakis(ss-lauryl thiopropionate), pentaerythritol tetrakis(p-hexyl thiopropionate), etc.

The synthetic resins stabilized by the present invention include low density polyethylene, high density polyethylene, linear low density polyethylene, chlorinated polyethylene, EVA resin, polypropylene, polyvinyl chloride, methacrylic resin, polystyrene, high-impact polystyrene, ABS resin, ACS resin, MBS resin, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyimide, polycarbonate, polyacetal, polyurethane, unsaturated polyester resin, etc.

The present invention will be explained by way of a Reference Example and Examples, but the invention is not limited by these Examples.

Reference Example 1 12.0 g 2,2,6,6-tetramethyl-4-piperidyl dithiocarbamic acid, 350 g water and 25 g ethanol were placed in a flask and were raised to a temperature of 98"C. for dissolution. To this solution, 100 ml ethanol containing 5.4 g iodine was drop-added in 45 minutes. After stirring at 85 - 95"C. for 9 hours, low boiling fractions were distilled off to obtain a dry solid. Three hundred grams water was added, undissolved matter was removed by filtration and sodium carbonate was added to the filtrate to adjust the pH to 9 - 10. Solids which separated out were collected by filtration, and after water-washing, were dried at 700C. 5.9 g bis(2,2,6,6-tetramethyl-4piperidyl)thiourea was obtained, which we designate Compound (I-1).

The same reaction was carried out using 1,2,2,6,6-pentamethyl-4-piperidyl dithiocarbamic acid, whereby bis(1,2,2,6,6-pentamethyl-4-piperidyl)thiourea was obtained, which we designate Compound (1-2).

Example 1 By blending the following composition by means of a mixer for 5 minutes and melt-blending the same between mixing rolls at 180 C., a compound was obtained, which was then shaped into a sheet of a thickness of 1 mm by a heat press at 210"C. The sheet was cut into a test piece having a size of 150 x 30 x 1 mm. The test piece was light-irradiated in a Sunshine Weather-O-Meter (light source: carbon arc; black panel temperature: 83 + 3"C., spray cycle: 120 minutes; spray time: 18 minutes) and was bent like a lobster at every 60 hours. The time until the test piece was broken was measured to evaluate the resistance to weathering.

The results are shown in Table 1.

Composition: Weight parts Non-stabilized polypropylene 100 Calcium stearate 0.1 2,6-di-t-butyl-4-methylphenol 0.05 Compound to be tested 0.2 In the Table, UVA-1 through UVA-8 show the following compounds: UVA-1 2-hydroxy-4-methoxybenzophenone, UVA-2 2-hyd roxy-4-n-octoxybenzophenone, UVA-3 2(2-hydroxy-5-methyl phenyl )benzotriazole, UVA-4 2(2-hydroxy-3-t-butyl-5-methyl phenyl )-5-chloro benzotriazole, UVA-5 2(2-hydroxy-3,5-dipentylphenyl)benzotriazole, UVA-6 ethyl-2-cyano-3,3'-diphenyl acrylate, UVA-7 bis(3,5-di-t-butyl-4-hydroxybenzyl phos phoric acid)monoethyl ester Ni-salt, and UVA-8 bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate.

TABLE 1 Resistance to No. Tested compound weathering (hers.) Examples of 1 1-1 2280 the invention 2 1-2 1980 Comparison 3 UVA-1 180 Examples 4 UVA-2 420 5 UVA-3 240 6 UVA-4 600 7 UVA-5 420 8 UVA-6 240 9 UVA-7 360 10 UVA-8 1800 11 No addition 120 Example 2 By blending the following composition by means of a mixer for 5 minutes and melt-blending the same between mixing rolls at 180"C., a compound was obtained, which was then shaped into a sheet of a thickness of 1 mm by a heat press at 2100C. The sheet was cut into a test piece having a size of 150 x 30 x 1 mm.After refluxing this test piece in water for 63 hours, the test piece was light-irradiated in the same way as in Example 1 in a Sunshine Weather-O-Meter (light source: carbon arc; black panel temperature: 83 + spray cycle: 120 minutes; spray time: 18 minutes) and was bent like a lobster at every 60 hours. The time until the test piece was broken was measured to evaluate the resistance to weathering.

The resuls are shown in Table 2.

Composition: Weight parts Non-stabilized polypropylene 100 Caicium stearate 0.1 2,6-di-t-butyl-4-methylphenol 0.05 Compound to be tested 0.2 TABLE 2 Resistance to No. Tested compound weathering (hrs.) Examples of 1 1-1 1680 the invention 2 1-2 1560 Comparison 3 UVA-2 360 Examples 4 UVA-4 480 5 UVA-8 180 6 No addition 120 Example 3 To a 25% urethane dope (constituting of 25 weight parts of polyurethane resin, 3.75 weight parts of dimethylformamide and 71.25 weight parts of tetrahydrofurane), one weight %, based on the polyurethane resin, of compounds to be tested was added. The dope was then coated 1.2 mm thick on a polyester film and was dried for one hour in a drier.The sheet thus obtained was stamped out with a No.3 dumbbell, and the test piece was light-irradiated in a Fade-O-Meter (light source: UV carbon arc; black panel temperature: 63 + 3"C.) for 60 hours or 120 hours. Thereafter, the test piece was subjected to tensile test (rate of pulling: 200 mm/min.; measurement temperature: 25"C.) to obtain its break strength retention.

The results are shown in Table 3.

TABLE 3 Break strength retention Tested No. compound 60 hrs. 120 hrs.

Examples of 1 1-1 83 61 the invention 2 1-2 79 56 Comparison 3 UVA-2 43 22 Example 4 UVA-5 56 30 Examples 5 UVA-8 66 40 6 No addition 30 16 Example 4 The following composition was melt blended between mixing rolls at 150 C. and was formed into a sheet having a thickness of 0.5 mm by means of a heat press at 160"C.

This sheet was light-irradiated for 1200 hours in a Sunshine Weather-O-Meter (light source: carbon arc; black panel temperature: 63 t 3"C.; spray cycle: 120 minutes; spray time: 18 minutes) to observe change of color.

Composition: Weight parts Polyvinyl chloride 100 Dioctyl phthalate 38 Epoxylated soybean oil 2 Ba stearate 1 Zu stearate 0.3 Compound to be tested 0.2 TABLE 4 No. Tested compound Change ofcolor Examples of 1 1-1 lightyellow the invention 2 1-2 lightyellow Comparison 3 UVA-2 brown spots Examples 4 UVA-3 yellow Examples 5 UVA-8 yellow 6 No addition dark brown

Claims (6)

1. A stabilized synthetic resin composition characterized in that the composition is composed of a synthetic resin blended with a hindered piperidine compound represented by the following structural formula:

wherein R stands for a hydrogen atom or a methyl radical.

2. The resin composition as claimed in Claim 1 wherein the hindered piperidine compound is bis (2,2,6,6-tetramethyl-4-piperidyl)thiou rea.

3. The resin composition as claimed in Claim 1 wherein the hindered piperidine compound is bis (1 ,2,2,6,6-pentamethyl-4-piperidyl )thiou rea.

4. The resin composition as claimed in Claim 1 wherein the synthetic resin is selected from the group consisting of low density polyethylene, high density polyethylene, linear low density polyethylene, chlorinated polyethylene, EVA resin, polypropylene, polyvinyl chloride, methacrylic resin polystyrene, high-impact polystyrene, ABS resin, ACS resin, MBS resin, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyimide, polycarbonate, polyacetal, polyurethane and polyester resin.

5. The resin composition as claimed in any of the preceding claims wherein the hindered piperidine compound is used in an amount of 0.01 to 5 weight parts for 100 weight parts of the synthetic resin.

6. The resin composition substantially as hereinbefore described with reference to the Examples.