DE2365644C3 - Stabilizer combination for polyoxymethylene - Google Patents

Description

HO

(CH ₂ L-CO-O-

in which R _{1 is} an alkyl radical with 1 to 6 carbon atoms, R _{2 is} a hydrogen atom or an alkyl radical with 1 to 6 carbon atoms, A is a di- to hexavalent, aliphatic hydrocarbon radical with 1 to 12 carbon atoms and m is zero or an integer from 1 to 6 and η corresponds to the valency of A, component (b) is an alkaline earth metal salt of an aliphatic mono-, di- or tricarboxylic acid with 2 to 9 carbon atoms or an araliphatic or aromatic carboxylic acid with 7 to 9 carbon atoms and component (c) a compound of the formula

NC - NH- C - NH- R

Il

NH

is, in which R is a hydrogen atom, a cyano group, an alkyl radical with 1 to 12 carbon atoms, a cycloalkyl radical having 6 to 12 carbon atoms or an aryl radical having 6 to 12 carbon atoms means, where the aforementioned alkyl, cycloalkyl or aryl radical in each case with 1, 2 or 3 hydroxyl groups can be substituted.

2. Stabilizer combination according to claim 1, characterized in that component (b) an alkaline earth salt of a mono-, di- or tri-basic hydroxycarboxylic acid with 2 to 9 carbon atoms is.

Carboxylic acids such as ricinoleic acid are obviously used with preference
It is also known that compounds of the formula

It is known to use polyoxymethylenes, i. H. Homo- or copolymers of formaldehyde or of cyclic ones Formaldehyde oligomers, e.g. B. trioxane, by adding stabilizers against the action of Stabilize heat and oxygen. In particular, there are molding compositions based on oxymethylene polymers known as a stabilizing additive, a combination of a metal salt and a nitrogen-free one organic carboxylic acid with 2 to 30 carbon atoms and a certain phenolic antioxidant from the group of parabisphenols, paratrisphenols and paratetrakisphenols (see US patents 34 84 399 and 34 84 400). The phenol derivatives mentioned are exclusively Hydroxyphenylalkyl ethers, and from the multitude of carboxylic acid salts are the salts of long chain

CH, -OCO-R '- <

-OH

R "

z. B. (3,5-Di-t-butyl-4-hydroxyphenyl) propionic acid pentaerythritol tetraester, are suitable as antioxidants for polyoxymethylenes (cf. JA-AS 26 196/69).

It is also known that molding compositions made from polyoxymethylenes can be obtained by adding a stabilizer system let stabilize that of (1) 0.005 to 4 percent by weight, based on the polyoxymethylene, Compounds of the formula

HO -

ICHj) ₁₁₁ - CO-O-

in which Ri is an alkyl radical with 1 to 6 carbon atoms, R _{2 is} a hydrogen atom or an alkyl radical with 1 to 6 carbon atoms, A is a di- to hexavalent aliphatic hydrocarbon radical with 1 to 12 carbon atoms, m is zero or an integer from 1 to 6 and η corresponds to the valency of A, and (2) 0.01 to 3 percent by weight, based on the polyoxymethylene, alkaline earth salts of carboxylic acids with 10 to 20 carbon atoms and / or alkaline earth hydroxides (cf. DT-OS 20 43 498).

The prior art mentioned does not reveal whether a combination of hydroxyphenyl carboxylic acid esters with alkaline earth metal salts of short-chain carboxylic acids is possibly particularly effective.
The invention now relates to a stabilizer combination for polyoxymethylenes, which consists of a mixture of (a) a phenolic stabilizer, (b) an alkaline earth metal salt of a carboxylic acid and (c) optionally another costabilizer and is characterized in that component (a) a connection

so the formula HO

(CH ₂ ) ,,, - COO-

in which Ri is an alkyl radical having 1 to 6, preferably up to 4 carbon atoms, R2 is a hydrogen atom or an alkyl radical having 1 to 6, preferably 1 to
Carbon atoms, A a di- to hexavalent, preferably di- to tetravalent, straight-chain! or branched, aliphatic hydrocarbons having 1 to 12, preferably 1 to 6 carbon atoms and m zero or an integer from 1 to
preferably zero, 1 or 2 and η d
Valence of A corresponds to component (b) e

Alkaline earth salt of an aliphatic mono-, di- or tri-carboxylic acid with 2 to 9, preferably 3 to 7 carbon atoms or an araliphatic nrW aromatic carboxylic acid with 7 to 9 carbon,
men and component (c) is a compound of the formula

NC —NH-C —NH-R

NH

in which R is a hydrogen atom, a cyano group, an alkyl radical having 1 to 12, preferably 1 to 6 Carbon atoms, a cycloalkyl radical having 6 to 12, preferably 6 to 8 carbon atoms or one Aryl radical with 6 to 12, preferably 6 to 8 carbon atoms, where the aforementioned alkyl, Cycloalkyl or aryl radical can in each case be substituted with 1, 2 or 3 hydroxyl groups.

The amount of component (a) used to stabilize polyoxymethylenes is 0.05 to 4, preferably 0.1 to 2 percent by weight, the amount of component (b) 0.01 to 3, preferably 0.1 to 2 Weight percent and the amount of component (c) 0.01 to 1 weight percent, each based on the Polyoxymethylene.

The stabilizer combination according to the invention can neither be removed from the conventional solvents Dissolve polyoxymethylene nor diffuse out of the polyoxymethylene when exposed to thermal stress out, so that the molding compositions stabilized in this way are particularly suitable for use at higher temperatures or in contact with solvents. The stabilizers used are colorless and the polyoxymethylenes discolor even after prolonged exposure to heat, light or alkaline substances Media not or only relatively little.

The particular advantage of the molding compositions stabilized with the stabilizer combination according to the invention is that they are better than known molding compounds in the injection molding process to mold parts with streak-free Have surfaces processed. Injection molded parts with completely smooth and are obtained from the molding compositions shiny surfaces. In part, there is also the mechanical strength and the coefficient of friction improved by the streak-free surface. This can be the case with technical parts that are subject to high loads exposed, or be an advantage for maintenance-free bearings.

Of the esters of ring-substituted araliphatic or aromatic carboxylic acids used in the context of the invention in the stabilizer combination as component a) are particularly suitable esters of araliphatic or aromatic monocarboxylic acids having 7 to 13, preferably 7 to 9 carbon atoms, the aromatic nucleus in the 4-position with a Hydroxyl group and in the 3- or 3- and 5-positions each substituted with an aliphatic alkyl radical having 1 to 4 carbon atoms, and straight-chain or branched, aliphatic, di- to tetravalent alcohols, eg. B. Ester der
a> - (3-tert-butyl-4-hydroxyphenyl) pentanoic acid,
ö- (3-methyl-5-tert-butyl-4-hydroxyphenyl) propionic acid,

3,5-di-tert-butyl-4-hydroxybenzoic acid,
(3,5-di-tert-butyI-4-hydroxyphenyl) acetic acid,
j3- (3,5-Di-tert-butyl-4-hydroxyphenyl) -nronic acid

pS-Di-isopropyl ^ -hydroxyphenyO-acetic acid with ethylene glycol, propanediol- (1,2), propanediol- (1,3), butanediol- {1,4),
Hexanediol (1,6), decanediol (l.lO),
1,1,1-trimethylolethane or pentaerythritol.

The magnesium, calcium, strontium and barium salts of are particularly suitable as alkaline earth salts

(1) saturated or unsaturated, aliphatic mono-, di- or tricarboxylic acids with 2 to 9, preferably 3 to 7 carbon atoms, e.g. B. of acetic acid, propionic acid, butyric acid, valeric acid, Caproic acid, enanthic acid, caprylic acid and pelargonic acid. also oxalic acid, malonic acid, Succinic acid, glutaric acid, adipic acid and suberic acid, as well as acrylic acid, methacrylic acid, Crotonic acid, isocrotonic acid, angelicic acid and tiglic acid, or of

(2) araliphatic carboxylic acids having 7 to 9 carbon atoms, e.g. B. phenylacetic acid and cinnamic acid, or from

(3) aromatic carboxylic acids having 7 to 9 carbon atoms, e.g. B. benzoic acid.

The alkaline earth salts of mono-, di- or tri-basic hydroxycarboxylic acids with 2 to are particularly suitable 9, preferably 3 to 7 carbon atoms, e.g. B. the calcium and magnesium salts of lactic acid, mandelic acid, Malic acid, citric acid and hydroxypivalic acid as well as salicylic acid.

The molding compositions preferably also contain co-stabilizers against the influence of heat and Oxygen, for example polyamides, amides of polybasic carboxylic acids such as malonic acid diamide, ureas and poly (N-vinyl lactams). In particular, are suitable as Costabilizers guanidine compounds of the formula

NC —NH-C —NH-R

Il

NH

in which R denotes a hydrogen atom, a cyano group, an alkyl radical having 1 to 12, preferably 1 to 6 carbon atoms, a cycloalkyl radical having 6 to 12, preferably 6 to 8 carbon atoms or an aryl radical having 6 to 12, preferably 6 to 8 carbon atoms, where the aforementioned alkyl, cycloalkyl or aryl radical can in each case be substituted with 1, 2 or 3 hydroxyl groups, e.g. B. cyanoguanidine, N-cyano-N'-methyl-guanidine, N-cyano-N'-ethylguanidine,
N-cyano-N'-iso-propylguanidine,
N-cyano-N'-tert-butylguanidine,
N-cyano-N'-dodecylguanidine,
N-cyano-N'-cyclohexylguanidine,
N-cyano-N'-benzylguanidine,
N-cyano-N'-phenylguanidine,
N-cyano-N'-hydroxyethylguanidine, N-cyano-N '- (2-hydroxyethyl) -guanidine or N, N'-dicyanoguanidine.

The costabilizer is optionally used in an amount of 0.01 to!, Preferably 0.1 to 0.5 percent by weight, based on the polyoxymethylene used. Furthermore, the molding compositions can also be known light stabilizers such as benzophenone, acetophenone or triazine derivatives. Other common additives like Dyes, pigments, reinforcing agents and fillers can also be added.

The stabilizers are used as a powder with commercially available mixers, for. B. dry mixers, into the polyoxy

methylene incorporated or in a suitable solvent, ζ. B. methanol, acetone or methylene chloride, dissolved and drawn onto the polymer with stirring. The solvent is then evaporated again.

Polyoxymethylenes which can be stabilized with the stabilizer combination according to the invention are Homopolymers of formaldehyde or a cyclic oligomer of formaldehyde, e.g. B. trioxane, its hydro>; yl end groups chemically, e.g. B. by esterification or etherification, are blocked, and Copolymers of formaldehyde or a cyclic oligomer of formaldehyde, preferably trioxane, wherein the copolymers in the main valence chain are oxyalkylene groups with at least two, preferably two to four adjacent carbon atoms. The comonomer share! in the copolymers is 0.1 to 50, preferably Ο, Ί to 15 percent by weight.

As compounds suitable for copolymerization with formaldehyde or cyclic oligomers of formaldehyde, preferably trioxane, are especially cyclic ethers and / or cyclic acetals and / or linear polyacetals are used. Cyclic ethers with 3 to 5 ring members are particularly suitable, preferably epoxides, also cyclic acetals with 5 to 11, preferably 5 to 8 ring members, in particular cyclic formals of α, ω-diols with 2 to 8, preferably 2 to 4 carbon atoms in the chain, their carbon chain at intervals of 2 carbon atoms can be interrupted by an oxygen atom, as well as linear polyformals.

In particular are compounds of the formula

CH ₂ - (CHR), - [0- (CH ₂ ) ..], .-

suitable, in which R is a hydrogen atom, an alkyl radical with 1 to 6, preferably 1 to 3 carbon atoms, which can be substituted with 1 to 3 halogen atoms, preferably chlorine atoms, an alkoxymethyl radical with 2 to 6, preferably 2 to 4 carbon atoms, a phenyl radical or a phenoxymethyl radical, χ an integer from 1 to 3, where y is zero, y is an integer from 1 to 3, where χ is zero and ζ is 2, and ζ is an integer from 3 to 6, preferably 3 or 4, where χ is zero and ^ is 1.

As cyclic ethers z. B. ethylene oxide and epichlorohydrin as well as propylene oxide, styrene oxide, cyclohexene oxide, Oxacyclobutane, phenylglycidyl ether and butanediol diglycidyl ether are used while as cyclic Formal examples, for example, 1,3-dioxolane, 1,3-dioxepane and 1,3,6-trioxocane and 4-chloro-triethyl-l, 3-dioxolane, 1,3-dioxonane and 1,3-dioxacycloheptene- (5) can be used.

The polyoxymethylenes used according to the invention are macromolecular; the values of their reduced specific viscosity (RSV), measured at 140 ⁰ C on a 0.5 weight percent solution of the polymer in

Table 1

γ-Butyrolactone, which contains 2 percent by weight of diphenylamine as a stabilizer, is 03 to 3.0, preferably 0.5 to 2 dl / g. The crystalline melting points of the above polyoxymethylenes are in the range of 150 to 18O ⁰ C.

The molding compositions stabilized with the stabilizer combination according to the invention can be used for all thermoplastic plastics usual processes, for. B. by injection molding, extrusion molding, extrusion blow molding,

ίο melt spinning or deep drawing, processing. she are suitable for the production of semi-finished and finished parts such as moldings, e.g. B. ribbons, rods, Bristles, threads, fibers, plates, films, foils, tubes or hoses, as well as household items, e.g. B. Bowls

ι _s or cups, and machine parts, e.g. B. housings or Gears. The molding compositions are particularly suitable for the production of injection molded parts which Have recesses, ribs or holes through which the flow of the molten mass in the Shape is disturbed.

Examples 1 to 12 and Comparative Examples A to C

An acetylated formaldehyde homopolymer (RSV value: 0.90 dl / g) is 1.0 percent by weight

Tetrakis-r> (3,5-di-tert-butyl-4-hydroxyphenyl) -propionyl-oxymethyl] -methane and 0.2 percent by weight of a magnesium salt of the acids listed in Table 1 intimately mixed and granulated on a commercially available extruder. On the dried granules, the

jo weight loss after 45 or 120 minutes of heating the sample in air at 230 ⁰ C determined. Further, before from the granules and after heating for 30 minutes in a closed mold at 230 ⁰ C for 2.5 mm thick, round pressing plates with a diameter of 4.5 cm

manufactured; the yellow coloration of the plates is then determined (yellow values) in a differential colorimeter (Colomaster device from Manufacturing, Engineering and Equipment Corp., Hatbore, Pa, USA).
Further, from the granules on a commercial injection molding machine (melt temperature: 200 ⁰ C; mold temperature: 8O ⁰ C; injection pressure and holding pressure: 45 bar; piston forward speed: medium) drop-shaped plates sprayed leading to the examination of possible streaking during the spray operation especially suitable are. The molded part, which according to the invention with a mixture of 1.0 percent by weight of tetrakis - [/ J- {3,5-di-tert-butyl-4-hydroxyphenyl) propionyl-oxymethy!] - methane and 0.2 percent by weight of the Magnesium salt of malic acid-stabilized polyoxymethylene molding compound is produced, shows no streaks, while the molding, which is made of a tetrakis - [/ J- (3,5-di-tert-butyl-4-hydroxyphenyl) with a mixture of 1.0 percent by weight propionyl oxymethyl] methane and 0.2 percent by weight calcium stearate stabilized same molding compound is produced, has clearly recognizable streaks.

The results of the tests are shown in Table 1.

example Magnesium salt of Weight loss after
45 min 120 min 3.3
2.5
2.9 Yellow value
before later Surfaces-
qualiläl of
Blown parts A.
B.
Γ Stearic acid
Ricinoleic acid
Arachidic acid 0.82
0.66
0.72 0.8
1.6
3.5 12.2
14.0
23.0 strong streaks
the same
the same

onset / ling Miigncsiumsal / der (weight ext in me (lelbwcrt later Surfaces- cispicl c | iialital of 4) min 120 well before 18.9 lormtcilen (<'/ ,.) 17.4 acetic acid 0.80 3.1 0.4 13.8 no streaks 1 Propionic acid 0.61 2.8 1.8 12.2 the same 2 Caproic acid 0.92 3.5 0.4 14.9 the same 3 Pelargonic acid 0.84 3.1 0.1 ! 8.3 the same 4th Lactic acid 0.75 2.9 0.7 25.0 the same 5 Malic acid 1.05 3.7 1.2 10.0 the same 6th Hydroxypivalic acid 1.22 4.1 1.4 11.4 the same 7th Malonic acid 1.17 4.3 0.1 25.0 the same 8th Adipic acid 0.97 3.5 0.1 17.1 the same 9 Salicylic acid 1.01 3.9 0.4 15.2 the same 10 Cinnamic acid 1.05 4.0 1.8 the same 11th Mandelic acid 0.91 3.4 0.0 the same 12th

Example 13 and Comparative Example D.

A copolymer of 98 percent by weight trioxane and 2 percent by weight ethylene oxide (RSV value: 0.82 dl / g) with 0.5 percent by weight 1.6-bis [ß- (3.5-

di-tert-butyl-4-hydroxyphenyl) propionyloxy] hexane
and 0.1 percent by weight of an alkaline earth metal salt are intimately mixed and granulated on a commercially available extruder. The weight loss after 120 minutes of heating the sample to 23O ⁰ C is determined in air to the dried granulate. Furthermore, the yellow values before and after heating for 30 minutes are determined according to Examples 1 to 12.

Furthermore, valve disks are made from the granulate under the conditions mentioned in Examples 1 to 12 sprayed, the surface condition of which is examined. From the molding composition according to the invention manufactured valve disks show a smooth, perfect surface, while the valve disks according to Comparative Example D fine cracks near the hole that make the valve disc inoperable.

Table 2

at
game Alkaline earth salt Yellow value by weight
loss
(%) before 1.1
0.8 later D.
13th Calcium ricinoleate
Calcium lactate
Table 3 2.8
2.6 Slabilisatnrkombiniuion
Art 17.1
15.8 example

Examples

A copolymer of 98 percent by weight trioxane and 2 percent by weight ethylene oxide (RSV value: 0.82 dl / g) with 0.5 percent by weight 1,6-bis- [j3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -hexane, 0.1 weight percent calcium lactate and 0.02 weight percent cyanoguanidine intimately mixed and on one commercial extruder granulated. The weight loss on the dried granules after 120 minutes Heating a sample in air to 230 ° C. is determined; it is 2.2 percent. The yellow values are also determined determined before and after heating for 30 minutes according to Examples 1 to 12; they are 0.6 and 12.4, respectively. From the Molded parts made from granules have a smooth, streak-free surface.

40 Example 15 and Comparative Example E

45 A copolymer of 98 percent by weight of trioxane and 2 percent by weight of ethylene oxide (RSV value: 0.82 dl / g) is intimately mixed with the stabilizers indicated below and granulated in a commercially available extruder. The weight loss is determined tigern according 45minü or 120 minutes of heating the sample to a "temperature of 23O ⁰ C under air on the dried granulate.

Weight loss ( ⁰ Ai)

after

Amount 45 min 120 min

(Gcw.-o / o)

\ l Ethylene glycol bis (3,5-di-t.butyl-4-hydroxy-

bcnzyl) ether

Calcium lactate 0.2 2.3 8.9

| 3 Ethylcnglycol bis (3,5-di-t-butyl-4-hydroxy-0.7

benzoic acid ester

Calcium lactal ° ^{2 n 7 2 0}

Example 16 and Comparative Example F

A copolymer of 98% by weight of trioxane and 2% by weight of ethylene oxide (RSV value: 0.82 dl / g) is used in each case intimately with the stabilizers given below

Table 4

mixed and granulated on a commercial extruder. The dried granulate is dei Weight loss after heating the sample to a temperature of 230 ° C. for 45 minutes or 120 minutes determined under air.

Example stabilizer or stabilizer combination On

crowd
(Wt .- «/«)

Weight loss (%)

after

45 min 120 min

F Tetrakis [j9- (3,5-di-t-butyl-4-hydroxy-phcnyi) -

propionyl-oxymethyl] methane

Tetrakis [, 9- (3,5-di-t.buiyl-4-hydroxyphenyl) -1.0

propionyl-oxymethyl] methane

Calcium dialeate 0.1

Cyanoguanidine 0.02

0.58

41

2.0

Claims (1)

Patent claims: 1. Stabilizer combination for polyoxymethylenes, consisting of a mixture of (a) one phenolic stabilizer, (b) an alkaline earth metal salt of a carboxylic acid and (c) optionally one further costabilizer, characterized that component (a) is a compound of the formula