DE2953528C2 - Process for roughening the surface of molded parts made from a polyacetal resin composition - Google Patents

Description

characterized in that the molded parts are immersed in an aqueous solution which Contains sulfuric acid

2. The method according to claim 1, characterized in that the sulfuric acid-containing aqueous Solution has a sulfuric acid concentration of 35 to 75% by weight.

3. The method according to claim 1, characterized in that the sulfuric acid-containing aqueous Solution also contains phosphoric acid.

4. The method according to claim 3, characterized in that the composition of the solution of sulfuric acid, phosphoric acid and water is shown in a sulfuric acid-phosphoric acid-water concentration diagram by the area that is to the right of a 15 wt% 96% Straight line a expressing sulfuric acid, above a straight line b, which connects the point 35% by weight aqueous solution dor 96% strength sulfuric acid and the point 45% by weight aqueous solution of 85% phosphoric acid, and below a straight line c, which connects the point 75% strength by weight aqueous solution of 96% strength sulfuric acid and the point 90% strength by weight aqueous solution of 85% strength phosphoric acid.

5. The method according to claim 3, characterized in that the roughening with a solution undertakes the sulfuric acid, phosphoric acid and water in a weight ratio of about 40: 25: 35 contains.

6. The method according to claim I _1, characterized in that the aqueous solution containing sulfuric acid additionally contains potassium dichromate.

7. Use of molded parts with a roughened surface according to claim 1 to 6 for electroplating or coating.

Plastics are generally very resistant to chemicals, and those made from them by injection molding or the like manufactured molded parts have a smooth surface, so that the surface by printing, coating, Deposition or the like difficult to decode or surface treatment by gluing with the aid to be subjected to an adhesive since polyacetal resins have a particularly low surface activity and no suitable solvent with an affinity for polyacetals is known, are decoration and Gluing their surfaces difficult to carry out, so that they are hardly in the current state of the art be used for purposes requiring these treatments. To put it the other way round: there

ίο Polyacetal resin has excellent mechanical properties has, it is mainly used for mechanical parts or the like in many cases, so that the Decorating its surface has not previously been required very often.

In the use of plastics, however, there has recently been an increased trend towards more versatile ones and more demanding uses, often requiring several requirements to be met, for example the function and appearance or the function and ability of the bond, the Tolerance was not absolutely necessary up to now, the trend is thus at the moment that good Surface machinability is also required when using polyacetals.

It cannot be said that the possibility of improving the surface machinability of Polyacetal resins have been intensively studied so far, but the applicant is aware that the machinability the surface to some extent

jo can be improved by treating the molded parts with an acidic solution or an antioxidant solution can. The acidic solutions used were p-toluene sulfonic acid, Camphor sulfonic acid, phosphoric acid, acidic ammonium sulfate and the like are suggested while being acidic Antioxidant mixtures of chromic acid and sulfuric acid have been suggested.

It is considered the goal of treatment with these solutions to create a rough surface by means of chemical etching Surface of the molded parts made of polyacetal resins and at the same time reactive groups on part of the polyacetal molecule due to the oxidizing effect of the Form solution. When trying to increase the effect of the surface treatment in this process improve, problems and difficulties arise, ζ. B. a disadvantageous change in the base material, i.e., the polyacetal resin, throughout the mass of the molding, cracking, etc. If on the other hand, treatment under conditions in which there is no adverse change in the base material occurs, the effect of the surface treatment is insufficient, so that a good one Processing of the surface is not possible. For these reasons, no molded parts have been made so far Polyacetal resin known to have sufficient surface workability for practical use.

The invention relates to a method for roughening the surface of molded parts from a Polyacetal resin compound

a) 100 parts by weight of a polyacetal resin,

b) 2 to 35 parts by weight of a carbonate, phosphate or acetate of a metal from group II des Periodic table or a mixture of these

h-i salts and

c) 0.01 to 20 parts by weight of a polymer or copolymer of a compound from unsaturated polyesters, alkyl esters of acrylic

acid and methacrylic acid, amides of acrylic acid and methacrylic acid, triallyl cyanurate, diallyl phthalate, vinyl acetate and divinylbenzene or a mixture of these polymers and copolymers and optionally
d) a heat stabilizer, antioxidant, UV absorber, antistatic agent, crystal nucleating agent and / or pigment,

which is characterized in that the molded parts immersed in an aqueous solution containing sulfuric acid.

The composition of the resin composition is important to this process; because by adding the Metal salts will form a roughened surface, which is suitable for surface finishing suitable, relieved. If a salt of a metal from Group II of the Periodic Table is in the from the Polyacetal existing closed phase dispersed it can easily be decomposed and removed with an acid, leaving its traces as roughened Surface left behind. The mean particle size the metal salts should expediently be in the range from 0.1 to 4.0 μm, in particular in the range from 0.5 to 2.0 μm their amounts are in the range from 2 to 35% by weight per 100 parts by weight of polyacetal resin, preferably in the range from 2 to 25 parts by weight.

Since when etching a molded part with a suitable acid, i. H. an acidic solution or an antioxidant solution, Rissbüdung occurs in the molded part itself and the mirror-like nature and the mechanical Properties of the plated product are greatly deteriorated when the acidic solution or Antioxidant solution is particularly strong, and also discoloration under unfavorable molding conditions of the molded part can occur and streaks through the thermal decomposition of the polyacetal resin Gas formed during molding may remain in the surface of the molded part the additional masses 0.01 to 20 parts by weight of a polymer or copolymers of a compound selected from unsaturated polyesters and alkyl esters of acrylic acid or methacrylic acid, amides of acrylic acid or methacrylic acid, triallyl cyanurate, diallyl phthalate, Vinyl acetate and divinylbenzene existing group or a mixture of these polymers and Copolymers. These are added to prevent cracking in molded parts, even if they are with a particularly strong acidic solution or oxidant solution can be etched, unu to during the shaping prevent deterioration in heat resistance that may occur when the resin composition Contains metal salts.

Optionally, the polyacetal resin composition can also contain various additives that are usually found in polyacetal resins can be used, for example heat stabilizers, antioxidants, UV absorbers, antistatic agents, Nucleating agents and pigments.

The molded parts can be produced from the polyacetal resin composition by customary processes, for example by injection molding, extrusion or pressing. The molded product has excellent Machinability of the surface and according to the invention is a treatment for roughening the Surface and can then be electroplated or coated, whereupon it is excellent Has surface properties.

According to the invention, acidic solutions are suitable for roughening the surface of the molded part obtained or oxidizing solutions that are able to decompose the metal salt present in the mass. From the From the point of view of handling, less volatile solutions, for example aqueous sulfuric acid solutions, mixed aqueous solutions of sulfuric acid and phosphoric acid, mixed aqueous solutions of Sulfuric acid and potassium dichromate and the like are used.

in When the polyacetal resin is made from a copolymer exists, the roughening of the surface can be sufficiently roughened with an aqueous sulfuric acid solution, a mixed aqueous solution of sulfuric acid and potassium dichromate or the like will. When the polyacetal resin is made of a homopolymer, an ideal course of roughening becomes reached the surface. Wonn a mixed aqueous sulfuric acid and phosphoric acid solution is used, the roughening of the surface is satisfactory regardless of whether the polyacetal is used is a copolymer or homopolymer, although the course is particular in the case of the homopolymer is satisfactory when using a mixed aqueous solution of sulfuric acid and phosphoric acid The proportion specified by the range shown in the figure is preferred below this is taking place for the use of 96% sulfuric acid and 85% phosphoric acid Explained with reference to the sulfuric acid-phosphoric acid concentration diagram.

The figure shows a graph showing the concentrations of sulfuric acid and phosphoric acid in the caustic acid solution, the abscissa being the content (%) of 96% sulfuric acid based on Water and, as the ordinate, the content (%) of 85% by weight phosphoric acid, based on water, is plotted are.

The concentration range according to the invention aqueous etching solution used is with reference

4Ii me explained on the figure which represents the area d- ^ r is bounded by the straight line which denotes the The 100% point of 96% sulfuric acid on the abscissa and the 100% point of 85% phosphoric acid on the ordinate and connects the two axes.

This area can be divided into the following parts:

1) Area to the left of line a:

The adhesive strength, ie the peel strength (N / mm) of a metal layer formed by subsequent plating after etching is very low and is less than 1 N / mm. In the figure, this corresponds to the area of low sulfuric acid concentration lying on the left-hand side of line a , namely 15% by weight of 96% sulfuric acid.

2) Area under line b:

The etching time for obtaining maximum bond strength is too la.ig (over 150 minutes at 40 ⁰ C are

f, o required) so that production management is poor. In the figure, this corresponds to the area that lies to the left under the straight line b , which connects the 35% point of 96% sulfuric acid and the 45% point of 85% phosphoric acid.

b5 det.

3) Top of the line c.

The etching time for obtaining maximum bond strength is too short (one minute or less at 40 ⁰ C),

that the stability is bad. In the picture this corresponds to the area that lies on the right above straight line c, which is the 75% point of 96% Sulfuric acid and the 90% point of 85% phosphoric acid.

All of the above-mentioned areas (1), (2) and 13) are technically unsuitable, while the area without ()), (2) and (3), ie the hatched area in the figure by the straight line a. b and c is the technically applicable range according to the invention. The content of 96% sulfuric acid is designated with "v" and the content of 85% phosphoric acid with ".". so the hatched area is the area bounded by the following formulas:

ν a l. \ is - - ν + 45

- ν f 9 (1

Furthermore, an aqueous solution, the total content of 96% sulfuric acid and 85% phosphoric acid 45 to 75% by weight and their content of 96% Sulfuric acid is 15% by weight, preferred. Further the part over in the hatched area

the straight line d which connects the 20% point of 96% sulfuric acid and the 90% point of 96% sulfuric acid and the 10% point of 85% phosphoric acid is particularly preferred.

According to the invention, the customary technical acids are suitable as sulfuric acid and phosphoric acid Question. Sulfuric acid with a concentration of 96% and phosphoric acid with a concentration of 85% are usually commercially available. The concentration range according to the invention was based on this Established the basis. If sulfuric acid and / or phosphoric acid with a different concentration is used it is necessary to use the acid or acids to be used after conversion based on their actual concentration.

The electroplating of molded plastic parts is well known and is used for ABS resins and the like. technically applied. These known methods can also be used for electroplating the polyacetal resin compositions be applied. For example, the method as described in Modern Plastics Encyclopedia. Pp. 1019-1021 (1967). carried out as follows:

1) Degreasing the molded parts:

The purpose of this measure is to remove grease from human hands or machine oil, which adhere to the surface of the molded part. Degreasing is done by dipping or steaming with l.i.l-trichloroethane. Degreasing can also done with normal washing machines.

2) roughening the surface:

The molded part is immersed in the above-mentioned acid. The immersion conditions vary with the type of molding and the composition of the acid, however, the combination of Temperature and time chosen so that the final plated product will be excellent Appearance (mirror-like texture) and approximately maximum and permanent adhesive strength or Has peel strength. Some examples of this are given in the examples below illustrated.

3) conferring electrical conductivity (sensitization, activation and electroless plating):

The molded part, the surface of which has been roughened in the described! .I NEN way, is in a

aqueous HCl solution, the SnCl; contains, and then in an aqueous HCl solution containing PdCb, submerged. In a preferred suitable method, it is mixed in one step aqueous HCI solution immersed, the SiiCb and PdCl? contains. In this process, Pd germs are deposited on the roughened surface in order to reduce the in the next process a thin layer of nickel is chemically formed, in this way the Surface of the molded part made electrically conductive.

4) Electroplating:

Electroplating is done to a thickness suitable for the purpose after the usual procedures, for example in the order f'ii / Ni / (r, carried out.

Weiin (Ims I ormieil from the polyacetal resin compound in etched in the manner described above and

i'p elcktroplatticTi, the adhesive strength is or AbrciBfusiipkcii; ler leveled layer about 1 N / mm or more, generally about 1.5 to 2.5 N / mm. That etched I ormieil also shows a surprising effect in treatments other than metal plating

;, tion, namely in the I all of the coating or bonding with an adhesive. This coating method is explained below. The molding is in the in the same way or in a similar way as for the Elcktroplatiiening degreased and on the surface

i'i roughened, after which the surface is dried well. Commonly used paints are then applied and baked for a certain period of time. The invention is further illustrated by the following examples. The production of the masses will

: ι only described for understanding.

Examples 1 to 13 and
Comparative examples 1 and 2

100 parts by weight of a commercially available acetal

v. homopolymer of general quality were with 8.7 parts by weight of a finely powdered calcium carbonate with an average particle size of 1.25 μm and of the compound mentioned in Table 1 and used as component (c) in the amount mentioned there in

5s of a rotary drum mixed. The mixture was kneaded and granulated with the aid of an ^{extruder set at 190 5 C.} The thermal stability was measured on these granules. A 3.2 mm thick plate was used as a test specimen from the

*> n granules produced

The plate was degreased with 1,1,1-trichloroethane and then etched according to the invention by placing it in a solution of 96% sulfuric acid ^{at 40 ° C. for 8 minutes.} 85% phosphoric acid and water in a weight ratio of 40: 25: 35 was immersed.

The etched plate was then plated in the usual way. It was then immersed in a commercially available acidic for a certain period of time. PdCh and SnCl ₂

containing solution for the ('refining of plastic fen and then in a 10% aqueous hydrochloric acid solution Immersed as an accelerator, then treated with a commercially available, electroless nickel bath and then immediately electroplated. The average thickness of the deposited layers oetrug 4½ μm for copper. 10), m for nickel and 0.1 μm with chrome. The properties of the clad product obtained in this way are in Table! called. They were determined using the following methods:

1) Adhesion strength or shell strength of the clad product:
Two parallel lines of fracture were drawn at a distance of 10 mm on the plated surface, and the deposited metal layer between the lines of fracture was peeled off at the right angle to the flat plate in order to measure the force necessary to tear it off.
2) Appearance of the plated product:

I nter a l.icliiqiitiit of 300 Luχ or melii the appearance was visible to the naked eye from a distance of 60 cm from the surface of the Test item examined. The criteria for the evaluation are given in the footnote to Table 1.

From Table 1, the improved heat resistance and excellent plating can be seen.

\ iMt! l ■ n.

Heivpicl

Polyacetalhar /. (ie «.- parts
('Alciumcarhonat (mean particle size 1.25 / iti). (ie «.- parts
Connecting line

(ic «-Toile

Wiirniebesliindigkeil (footnote I) Delicious non-solitary compound Detection method (solvent extraction or smell ι

See the plated product (Footnote 21

Adhesion strength of the plated
Product. N / mm

I)

r-,

loo

8.7

100

8.7

unsaturated methyl polyester acrylate
(Footnote 5)

n, X7 o.oi

O O

(Methanol / (methanol
Toluene)

D O

2.3

1.6

100
8.7

Athyla cry hit

0.76

1.8

100

8.7

Methyl methane rylate 0.87

(Methanol) (methanol)

Table I (continued)

example

Polyacetal resin. Parts by weight

Calcium carbonate (mean particle size 1.25 im). Parts by weight
link

Parts by weight

Heat-resistant wedge (footnote Ii Remaining unreacted compound detection method (Solvent extraction or odor)

Appearance of the plated product C

ί footnote 2;

Adhesion strength of the plated L6

Product. N7mm

100 HV 100 100 KX) 8.7 8.7 8.7 8.7 8.7 Ethyl mine
acryiate Acrylamide Methacrylic
amide Triallyl
cyanural
(Footnote 3) Diallyl
phthalate
(Footnote 3) 0.01 0.8 ' 0.87 6.10 0.87 O O O O ι methanol ι (Gerach) (Odor) (Odor) (Odor)

2.0

2.1

1.6

I dragonfly I (cake seedling)

IO

Hcis | ijel

IO

12th

Polyacctalhar /. Part by weight c 100 100 H) O

Calcium carbonate (medium particles- 8.7 8.7 8.7

larger than 1.25 µm). Parts by weight

Compound vinyl acetate

13th

100
8.7

Parts by weight 0.87

Heat resistance (footnote I) O

Remaining non-converted connection -

Detection method (solvent- ((ieruch) ((ieruch)

extraction or (ieruch)

Appearance of the plated product O 'j J

(Tuss note 2)

Adhesion strength of the plated 1.7 2.1 2.2

Product. N / mm

llivinylben / ol polyvinyl acetate unsaturated acrylic

(Note 4) Polyester amide

(TiIHiIoIe 5)

0.87 0.87 0.50 0.40

'~> OO "i

(Smell)! Smell)

O;

2.1 2.1

Footnotes to Table 1:

1> O Injection molding is perfectly possible under normal conditions.

Injection molding is possible without practical problems, but the range of suitable conditions is somewhat narrow. Δ During the injection molding process, streaks form due to the decomposition of the Ilar / .es. * Extrusion is impossible

2) Appearance was evaluated with the naked eye according to the eradicating criteria. O mirror surface without cracks.

Δ Dark image, but the face is reflected; no education. <No reflected image of the face. Crack formation.

(In the following tables, the same symbols clic have the same meanings as described above.)

31 (1.20 parts by weight (Example 8) and 0.04 (iew. Parts (Example ')) 2. ^ - Dimethv 1 2.5-di (terl.-biitylpero \> Ί-hex.in was': n as a polymerization initiator added.

4) Degree of polymerization 200. The other compounds were chemically pure.

5) Mixture of "0% by weight" of a polyester prepolymer of isophthalic acid / maleic anhydride / diethylene glycol in a molar ratio of 1/1/2 with an average degree of polymerization of 10 and. '(Kiev ^11th styrene as crosslinking agent.

Examples 14 to 17 and Comparative Examples 3 and 4

100 parts by weight of the acetal homopolymer of the previous examples were with 8.7 parts by weight of magnesium carbonate (mean particle size 2 to 3 μm), Barium carbonate (mean particle size 2 μm), barium acetate (mean particle size 3 μm) or calcium hydrogen phosphate (mean particle size 2 to 3 μm) instead of calcium carbonate and as a reactive compound a certain amount of an unsaturated one Polyester (mixture of 70 parts by weight of a polyester prepolymer, prepared from isophthalic acid, maleic anhydride and diethylene glycol (molar ratio 1: 1: 2), average degree of polymerization 10, and 30 parts by weight of styrene as crosslinking agent) mixed in a drum mixer, whereupon the mixture in the same Way, as described above, was kneaded and granulated in the extruder.

The heat stability of the granules was measured. From the granules, a plate was placed on the plate in Example 1

manufactured and plated to the

To study properties of the plated product. The heat resistance of this polyacetal resin compound

sen and the properties of the clad products mentioned in table 2

(All of the above metal salts were

* i chemically pure. The barium acetate was after

Grinding in the mortar used while the other Salts used in the form in which they were present

became.)

Il

Table 2

Polyacetalhar /. dew. parts
Magnesium carbonate
(mean particle size
2 to 3 -im), dew.-parts
Harium carbonate
(mean particle size

2 ι m). dew parts

Barium Aceta '.
(mean particle size

3 im), Ciew. Parts

1I egg around hydrogen phosphate

/ mi ti Io rp Tpilrh ^ narnUt " ¹
- · - - ■ -. -.....-. . _t .

2 to 3 jm). dew. parts
Unsaturated polyester. dew. parts extrudability

Heat resistance

Appearance of the plated product Adhesion strength of the deposited Metal layer. N / mm

Comparative Hei Comparative With- With- With-

example .1 · <ρίοΙ 14 example 4 game 15 game Ki game 17

KH) 8.7

KKl
8.7

100

8.7

KK)

P.7

100

8.7

1.6

100

8.7

- 8.7 violent 10.0 0.15 0.8 ', violent Well Schäui.ien Well Well Well Foam X X O _ O O O _ O O O O

Examples 18 to 20 and Comparative Examples 5 and 6

100 parts by weight of the polyacetal resin of the previous Examples were made with 11.1 parts by weight of calcium carbonate with the mean particle sizes stated in Table 3 and 1.1 parts by weight of that stated in Table 1 mixed unsaturated polyester. The obtained resin composition became that described in Example 1 Way plated. Dir.- Properties of the clad Products have been identified.

The properties of the clad products are shown in Table 3.

Table 3

Comparative example
example 5 *) 18

19th

20 ")

Comparative example 6

Mean Particle size of the calcium carbonate, μτη

Heat resistance
Appearance
Adhesion Strength, N / mm

0.08

1.0

1.25

3.6

5.0

O O O O O O Δ X 2.0 2.0 1.5 1.0

*) Extruding wa ^r impossible.

") The product is suitable for applications where good looks are not absolutely necessary.

Examples 21-23 and Comparative example 7

The same etched plate as in Table 3 was used. After the etching, the plate was made with Water washed well, air dried, coated with a commercially available paint Acrylic resin base coated and then baked at 150 ° C for 30 minutes. The adhesive strength of the applied The paint film was tested by placing a pressure-sensitive adhesive strip on the surface, on the grid cuts Squares 3.2 mm long had been applied, pressed and then the adhesive tape was demolished. The results are given in Table 4

Table 4 example

21 Comparative Example 7

1.0

Mean Particle size of the calcium carbonate, at the

Adhesive wedge of the paint film

shine

Criteria for the assessment of the adhesive strength:

O no change at all.

O Partial detachment on the edge parts.

x The proportion of detached squares is 20% or less.

xx Fas! all squares peel off.

1.25

3.6

5.0

O O O X glittering glittering glittering not glittering

Examples 24-27 and Comparative Examples 8-10

The same calcium carbonate as in Example 1 (mean particle size 1.25 μm) was used and the plate in the manner described in Example 1

Table 5

plated but the amount of calcium carbonate was varied as shown in Table 5. Furthermore, the unsaturated polyester in an amount corresponding to 10% of the calcium carbonate (parts by weight) was added The results are given in Table 5.

Comp.- Comp.- at at at at Comp.- example example game game game game example 8th 9 24 25th 26th 27 10

Polyacetal resin, parts by weight
Calcium carbonate (mean particle size 1.25 µm), parts by weight

Unsaturated polyester, parts by weight heat resistance
Properties before plating Tensile strength, N / mm ²

Elongation (between the

Clamps,%)

Flexural strength, N / mm ²

Notched Izod impact strength,
Nm / cm
(kg cm / cm)

Appearance of the plated product Adhesion strength of the deposited Metal layer, N / mm

Note: In the case of Comparative Example 10, the resin was decomposed during extrusion.

68.6 18

103

3.1

0.31
O

67.7
16

102

100
8.7

0.87
O

63.7
12th

102

17.6

101

25.0

100

0.6 0.6 0.5 0.5 0.4 0.4 (6) (6) (5) (5) (4) (4) X X O O O O 0.7 0.9 1.5 2.3 2.3 2.0

42.9

1.76 2.5 4.3 © O X 58.8 56.9 - 9 8th _

Examples 28 to 31 and Comparative Examples 11 and 12

The experiment described in Examples 25 to 27 and Comparative Example 8 was repeated, but with each other a commercially available acetal copolymer (general purpose resin) was used. The results obtained are ir Called Tiiibelle 6.

Table 6

Compare-heispie!

example
28

29

Compare example 12

Polyacetal resin. Parts by weight 100 100 100 100 100 10 (1

Calcium carbonnt (mean particle size 0 8.7 17.6 25.0 33.3 42.9

1.25 in). Parts by weight

Continue Tune

Comp.- example 29 30th .11 Comp.- example! I. 28 1.76 2.50 3.33 example 12 Unsaturated polyester, parts by weight 0 0.87 O © O 4.29 Heat resistance © © O O Δ Δ Appearance of the plated product O O 2.1 1.8 1.5 X Adhesion strength of the deposited 0.2 1.3 1.0 Metal layer (N / mm)

Examples 32 to 34 and Comparative Example 13

The experiment described in Example 25 was repeated, except that the amount of unsaturated polyester was used was varied. The results obtained are shown in Table 7.

Table 7

example 33 34 Comparison 32 100 100 example 13 Polyacetal resin (homopolymer), 100 100 Parts by weight 8.7 8.7 Calcium carbonate (mean particle size 8.7 8.7 1.25 μπι), parts by weight 10 15th Unsaturated polyester, parts by weight 0.87 O O 25th Heat resistance © 58.8 55.9 X Tensile strength, N / mm ² 63.7 13th 13th 51 Elongation (between the clamps),% 12th 88.3 83.4 14th Flexural strength, N / mm ² 102 72.6 Notched Izod impact strength, 0.4 0.3 Nin / cm 0.5 (4) (3) 0.2 (kg cm / cm) (5) (2)

Examples 35 to 40 and Comparative Examples 14 to 18

An identical 3 mm thick plate as in Example 1 was plated in the manner described in Example 1, wherein however, the composition of the etching solution was varied as shown in Table 8. The adhesive strength of the deposited metal layers are given in Table 8.

Table 8

example 36 37 35 30/35 32/10 96% sulfuric acid / 40/25 85% phosphoric acid (Parts by weight) *) 8th 70 Optimal etching time 8th (40 ⁰ C x minutes) 2.0 1.6 Adhesion Strength, N / mm 2.2

39

40

Comparative Example 14 15 16

17th

25/55 45/0 60/0 20/0 10/15 20/15 76/24 80/0

2.0

50

1.5

1.6

800

1.0

1000 600

0.4

1.1

1.9

*) If the sum of the (ic «.- parts was less than 100. Wasso: was added until the total weight reached KX1 parts by weight.

Example 41

An identical 3 mm thick plate as in Example 29 was immersed in an etching solution for 12 minutes at 40.degree below composition dipped

and then electroplated in the manner described in Example 29. The deposited metal coating had an adhesive strength of 1.3 N / mm.
Composition of the etching solution:

17 18

96% sulfuric acid 55 parts by weight machinability of the surface obtained, so that the

Potassium dichromate 4 parts by weight application of the resins is further expanded.

Water 45 parts by weight For example, metal moldings in which

both functional and decorative properties

As the above examples show, ί are required, replaced and very heavy weight losses

Polyacetal resin compositions can be achieved by etching the molded parts from reductions and cost savings.
Acetal resin compounds products with excellent

For this] sheet of drawings

Claims (1)

Patent claims: 1. A method for roughening the surface of molded parts made of a polyacetal resin composition a) 100 parts by weight of a polyacetal resin, b) 2 to 35 parts by weight of a carbonate, phosphate or acetate of a group II metal of the periodic table or a mixture of these salts and c) O ₁ Ol to 20 parts by weight of a polymer or copolymer of a compound from the group consisting of unsaturated polyesters, alkyl esters of acrylic acid and methacrylic acid, amides of acrylic acid and methacrylic acid, triallyl cyanurate, diallyl phthalate, vinyl acetate and divinylbenzene or a mixture of these polymers and Copolymers and optionally d) a heat stabilizer, antioxidant, UV absorber, antistatic agent, nucleating agent and / or pigment,