DE4311387C2 - Better washable impregnating liquid and its use - Google Patents

Description

The invention relates to an impregnating liquid (Meth) acrylate-based and their use in one Impregnation.

Porous objects, in particular metal castings or Sintered metal pieces are usually with a Impregnating sealed. This is necessary to the articles are resistant to liquid or to make gas pressure, as in use, eg. B. at Engine or transmission parts, occurs. By the Impregnation on the one hand on the surface of pores to be impregnated filled and on the other hand, continuous pores safely be closed. Especially the latter cause leaks in case of insufficient closure, the to a failure of the corresponding part in operation to lead.

For over 20 years, various procedures for Filling or closing of such pores known, the especially in cold impregnation and Subdivide warm impregnation. In the Cold impregnation, z. B. described in EP-A 0 421 567, 0 101 267, the cure is either by filling the pores with a curable Monomer mixture and subsequent Surface treatment with a catalyst or by Fill the pores with an inhibited in air Impregnating and curing this Impregnating fluid with exclusion of air carried out.

In another procedure, the pores with filled with a thermosetting impregnating agent and in Hardened hot water. This method is u. a. described in DE 27 18 770 A and DE-PS 19 26 126.

All these methods have in common that filling the Pores usually by immersion in the Impregnating liquid, if necessary under application of vacuum, and then washing off the impregnating liquid is performed from the surface of the object, the cure takes place only afterwards. Just washing the impregnating liquid from the Surface causes problems, because the Impregnating on the one hand not too good be water soluble, otherwise the pores be washed free, and on the other hand the Impregnating fluid from the smooth surface of the Object as completely as possible be washed should, so that no resin film on the surface of Forms objects. Difficult surfaces are especially precision bores, into the cylinder or Bearings are used, and tapped holes. Especially in the latter lead resin residues in Screwing in a screw to burst the Threaded bushing. A good impregnating agent should thus after curing to a temperature stable and lead solvent-resistant resin as possible and before curing from the surface of the impregnating object be easily washable, the latter already by mere immersion in Water should take place.

The object of the present invention is a Impregnating agent for cold and warm curing should be suitable and in particular by the Surface of the object to be impregnated easily washing and its use in a corresponding Impregnation.

This task is solved with a Impregnating liquid according to claim 1. This Impregnation fluid can according to her Purpose with different mixed polymerization-influencing components or after the pore filling are treated, wherein especially the thermosetting ones polymerization-influencing components preferred are.

The impregnating liquid according to the invention contains

• A. in water at least partially soluble (meth) acrylate: 50-85 wt .-%, consisting of
  • a) in water to at least 20 wt .-% of soluble (meth) acrylate: 0-85 wt .-% and / or
  • b) in water to at least 5 wt .-% and less than 20 wt .-% of soluble hydroxyalkyl (meth) acrylate: 0-80 wt .-%
• B. ethylenically unsaturated Monomer with C₈-C₂₀-alkyl radical: 4-40% by weight
• C. surfactant: 4-40% by weight, possibly
• D. copolymerizable monomers, limited to 5% by weight, possibly
• E. crosslinker, limited to max. 30% by weight, such as possibly
• F. a radical generator and a Inhibitor, with the A / B ratios between 1.25 and 10 lie

and is characterized that the individual components to each other in such a way are tuned that 1 ml of the impregnating liquid from about 10 cm high for 1 min in 50 ml of water Temperature dropped 90 ° C, at the latest after another 15 s to at least 90% emulsified.

This impregnating liquid finds particular Use for impregnating a porous solid Body, such as metallic castings or sintered parts.

Particularly good washability results in use of component A to 60-80 wt .-%. In addition, the Component Aa) is preferred, since in interaction this component with the component B the best Emulsifiability of a surface of a too adhering to the impregnating article Impregnating gives.

Usually the limitation of crosslinkers is advantageous, otherwise the polymer will become too brittle and In addition, the washability significantly decreases. This especially applies if the component Ab) is used comes, especially if this is the vast majority the component A makes. That's why Crosslinkers, if used at all, normally at max. 30 wt .-%, advantageously to max. 10 wt .-% and in particular the use of (meth) acrylic crosslinkers to max. 6% by weight limited. It is also in the use of the Component Ab), especially in their predominant Use, advantageous if the component B at max. 35 wt .-% is. Generally will be particularly advantageous the component B used to 5-20 wt .-%.

Usually, for component C 4-20% by weight advantageous, when using the component Ab), especially when this component predominates, is a slight increase in the lower limit of component C, d. H. at least 5% by weight, preferably.

The impregnating liquid according to the invention contains a balanced relationship between water-soluble (Meth) acrylates and (meth) acrylates with high hydrophobic portion. Especially if the Component Aa)  outweighs are A / B ratios between 1.25 and 10 are advantageous, with Ratios 2 and especially 2.5 and 7 and in particular 5 best washability is achieved. According to these circumstances, also shift the upper and lower limits of components A and B.

The components A, b and C are dimensioned so that the Impregnating liquid is easily washable and in particular a self-emulsifying mixture is available. Self-emulsifying means that the Impregnating in water, possibly elevated Temperature, spontaneously emulsified. This allows one easy rinsing from outside to one impregnating body more adhesive Impregnating liquid, which is in pores of the impregnating body Impregnating liquid remains in these and subsequently, z. B. by heating, polymerized can be. Suitable bodies are in particular Castings or sintered parts of metal, with pores below 0.2 mm i. d. R. after impregnation and Pores between 0.2 and 0.5 mm after a few Impregnations are closed. Larger openings, like tapped holes, stay free.

If desired, the impregnating liquid can still contain further copolymerizable monomers, as long as Washability with water, polymerizability and Resistance of the polymer by this not is impaired. Usually these are additional comonomers to at most 5% by weight limited.

For component Aa), such (meth) acrylate compounds are used Consider that with the others Components are miscible. These are in particular Alkyl esters with one or more hydroxyl groups or (Meth) acrylic esters of lower polyalkoxy compounds and aminoalkyl (meth) acrylates. The Amino (meth) acrylates can be primary, secondary, tertiary or ammonium compounds, d. H. bear corresponding substituents. The hydroxy groups can be primary, secondary or tertiary. Especially Advantageously, such compounds Aa) are used, at least 35% by weight in water (i.e., at least 350 g Aa) / kg solution) and in particular at least 50 wt .-% are soluble. Preferred compounds are Hydroxyethyl (meth) acrylate, di-, tri-, Tetraehtylenglycolmono (meth) acrylate, Hydroxypropyl acrylate, aminoalkyl (meth) acrylate.

The impregnating liquid is preferably with such polymerization-influencing components offset that from the entire mix one make thermosetting impregnating liquid. Suitable are additions of radical formers and Inhibitors, wherein as a radical generator in particular Azo connections, like

2,2'-azobisisobutyronitrile (AIBN, AZDN),
1,1'-azobis (1-cyclohexanecarbonitrile) (CHDN),
2,2'-azobis (2,4-dimethylvaleronitrile) (DMVN),
2,2'-azobis (2-methylbutyronitrile),
4,4'-azobis (4-cyanopentanoic acid)
Dimethyl-2,2'-azobisisobutyrate.

In principle, peroxydic catalysts can also be used be used, such. B. benzoyl peroxide, Methyl ethyl ketone peroxide, various alkyl peresters, Cumene hydroperoxide. These radical formers will be usually to max. 10% by weight of the total mixture added, the usual are 0.1-5 wt .-%, in azo compounds 0.01-2% by weight. To a premature To prevent polymerization, mix also usually added inhibitors, wherein this usually already in the monomer mixture are included. For thermosetting systems, the Catalyst together with the inhibitor in the Be included monomer mixture, wherein at appropriate tuning of the components this Mixture is storable for months. As inhibitors In particular, quinone compounds such as Hydroquinone monomethyl ether (MEHQ), β-naphthoquinone and p-benzoquinone; Phenols, such as p- or m-cresol; sterically hindered phenols, such as 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butyl-hydroquinone.

As component C are not reactive and reactive Surfactants or detergents into consideration, d. H. also those that contribute to the radical polymerization contain a qualified group. Particularly suitable Surfactants are anionic or nonionic surfactants and mixtures thereof, wherein the surfactant with the others Components should be miscible and the polymerization should not hinder. Suitable surfactants can, as in U.S. Patent 4,069,378. Examples of surfactants are polyalkoxylated C₈-C₂₀-alcohol, polyalkoxylated (substituted) Aromatic, polyoxyethylene-polyoxypropylene block copolymer, polyalkoxylated Alkylacetylene alcohols or glycols. Usually is the polyalkoxylated group is a polyethylene glycol and the hydrophobic residue is preferably linear, with a certain branching usually not disturbing and especially in the case of substituted aromatics is not a problem. The substituted aromatic contains usually a C₄-C₁₈ radical. Such surfactants are under the trademarks Siponic®, Igepal®, Arylpon®, Pluronic®, Arkopal®, Surfynol® available. As a surfactant are further still suitable linear or branched primary or secondary C₁₂-C₁₈ alcohols, C₈-C₁₂-alkylphenols, terminally blocked ethoxylates, in particular with Benzyl, phenyl or methyl as end group, higher Fatty acids, fatty acid ethanolamides, fatty acid amines, Fatty acid esters of polyhydroxy compounds. The Degree of polymerization of the polyglycol ether chains relatively uncritical, depending on the impregnated Subject, polymerization or Washability, the surfactant can be varied. Out the surfactants mentioned, as in EP-A 0 101 267 described, a corresponding surfactant with reactive Group are made.

To the group of at least partially water-soluble Components (A) belong in addition to those already mentioned N, N-dimethylaminopropyl (meth) acrylamide, 2-trimethylammoniomethyl (meth) acrylate chloride, Hydroxypropyl methacrylate.  

The components A can also act crosslinking, wherein a crosslinking fraction typically below 30% by weight in A lies. Preference is given to non-crosslinking compounds.

As component B come ethylenically unsaturated Monomers with a C₈-C₂₀-alkyl radical used, wherein for the ethylenically unsaturated radical (Meth) acrylate is preferred. Suitable compounds are in particular mixtures in terms of Alkyl radical. Examples are in particular the C₁₀ bis C₁₄-esters of (meth) acrylic acid, in particular with typical homologous distribution of the commercial Products. Individual examples are lauryl methacrylate, Dodecyl acrylate, decyl acrylate, decyl methacrylate.

As other crosslinkers can be used for example divinylbenzene, maleic acid diallyl ester, Di-, tri- and tetraethylene glycol di (meth) acrylate, Ethylene glycol di (meth) acrylate, allyl (meth) acrylate, Trimethylolpropane tri (meth) acrylate. In brackets set name, such. B. (meth), means that this substituent is optional.

The invention also relates to the use of Impregnating fluid in a process for impregnation a porous solid article, in particular a casting or sintered metal parts, by filling the pores with a polymerizable impregnating liquid and Polymerizing the impregnating liquid in the pores, at the containing the pores with an impregnating liquid

• A. in water at least partially soluble (meth) acrylate: 50-85 wt .-%, consisting of
  • a) in water to at least 20 wt .-% of soluble (meth) acrylate: 0-85 wt .-% and / or
  • b) in water to at least 5 wt .-% and less than 20 wt .-% of soluble hydroxyalkyl (meth) acrylate: 0-80 wt .-%
• B. ethylenically unsaturated Monomer with C₈-C₂₀-alkyl radical: 4-40% by weight
• C. surfactant: 4-40% by weight, possibly
• D. copolymerizable monomers, limited to 5% by weight, possibly
• E. crosslinker, limited to max. 30% by weight, such as possibly
• F. a radical generator and a Inhibitor, with the A / B ratios between 1.25 and 10 lie,

be filled.

The impregnating liquid used in the process can have all the details described above, wherein in particular the use of a Impregnating liquid is advantageous before the Filling the pores already contains a hardener system. The Hardener system is advantageously a combination of Radical generator and an inhibitor. Such Hardener system can be long before the application of Impregnating be mixed in this, since such impregnation liquid for months Room temperature is storable.

Usually, the pores of the porous Item by diving in the Impregnating and applying a vacuum (usually approx. 1-3 mbar over approx. 5 min). The Impregnating liquid usually has one Viscosity of about 1-1000 mPa · s, in particular 5-200 mPa · s. The inventive Impregnating has in the impregnation process the advantage of being particularly easy to wash without that the filled pores are washed free again.

For rinsing the outside of the to be impregnated Object adhering impregnating liquid is this simply dipped in water (about 20 ° C) and taken out again. After about 3-10 times diving is removes the externally adhering impregnating liquid, a spraying, a longer stay or other Measures are i. d. R. not necessary.

Subsequently, the article is in hot curing in 70 ° C hot water immersed (usually about 90 ° C), where the impregnating liquid in the pores usually cured after 10-12 min.

The invention will be described below by way of examples detailed.

Example 1 (all figures in parts by weight)

HEMA (hydroxyethylmethacrylate) 50 parts 2-ethylhexyl 40 parts alkylphenol 10 parts AIBN (2,2'-azobisisobutyronitrile) 0.1 part MEHQ (hydroquinone monomethyl ether) 250 ppm

are mixed together. The mixture is used for the following tests:
Emulsifiability in cold and warm water, elasticity testing of the polymer, impregnation of an aluminum casting (gearbox).

The emulsifiability is determined by a drop test certainly.

The drop test provides a visual assessment of the Emulsifying properties and is used to determine the Washing behavior of impregnating media. For this purpose, a 3-liter beaker of low form (Height 210 mm, A ⌀ 150 mm to three quarters filled with water and heated to 90 ± 2 ° C. The beaker filled with water serves as a hardening bath. In the hardening bath is a test tube of simple form (200 x 30 mm, in which 50 ml of water are presented (about half full), to the top immersed.

Above the test tube opening is a microburette (Hirschmann glass, 2 ml, 0.01 ml Subdivision, 0.01 ml tolerance). The Distance opening microburette to the water surface in Test tube is about 10 cm, the burette is with filled the impregnating medium to be tested. Once the water in the test tube has reached 90 ° C, 1 ml of impregnating liquid is dripped out of the burette to (within 1 min).

The behavior of the entering in the liquid Droplet is observed through the beaker. The  Water in the test tube is not stirred.

15 s after the end of the dropping must Impregnating liquid must be at least 90% emulsified.

When impregnating the Eindrehbarkeit of Screws and tightness (continuous pores) certainly.

For elasticity, a polymer of about 20 g Impregnating made, wherein the obtained Polymer should respond elastically to finger pressure. On This polymer is also heated to 200 ° C over a period of 12 h the weight loss certainly, this should be below 2% and especially below 1% lie.

Example 2

HPMA (hydroxypropyl methacrylate) 80 parts LMA (lauryl methacrylate) 10 parts alkylphenol 10 parts AIBN 0.1 part MEHQ 250 ppm

are mixed together and the mixture like investigated under Example 1.

Example 3

HEMA 70 parts LMA 20 parts alkylphenol 10 parts AIBN 0.1 part MEHQ 250 ppm

are mixed together and the mixture like investigated under Example 1.

Example 4

HEMA 50 parts LMA 18 parts dodecyl 22 parts alkylphenol 10 parts AIBN 0.1 part MEHQ 250 ppm

are mixed together and the mixture like investigated under Example 1.

Example 5

HEMA 65 parts LMA 20 parts TEDMA (triethylene glycol di (meth) acrylate) 5 parts alkylphenol 10 parts AIBN 0.1 part MEHQ 250 ppm

are mixed together and the mixture like investigated under Example 1.

Example 6

HEMA 62 parts LMA 20 parts maleate 8 parts alkylphenol 10 parts AIBN 0.1 part MEHQ 250 ppm

are mixed together and the mixture like investigated under Example 1.  

Example 7

HEMA 50 parts LMA 20 parts laurate 20 parts alkylphenol 10 parts AIBN 0.1 part MEHQ 250 ppm

are mixed together and the mixture like investigated under Example 1.

The results are listed in the table.

Claims (8)

1. Impregnating liquid containing

• A. in water at least partially soluble (meth) acrylate: 50-85 wt .-%, consisting of
  • a) in water to at least 20 wt .-% of soluble (meth) acrylate: 0-85 wt .-% and / or
  • b) in water to at least 5 wt .-% and less than 20 wt .-% of soluble hydroxyalkyl (meth) acrylate: 0-80 wt .-%
• B. ethylenically unsaturated monomer with C₈-C₂₀-alkyl radical: 4-40 wt .-%
• C. Surfactant: 4-40% by weight, optionally
• D. copolymerizable monomers limited to 5 wt .-%, optionally
• E. crosslinker, limited to max. 30 wt .-%, and optionally
• F. a free radical generator and an inhibitor, wherein the A / B ratios are between 1.25 and 10,

characterized in that the individual components are coordinated so that 1 ml of the impregnating liquid from about 10 cm height dropwise over 1 min in 50 ml of water at 90 ° C, at least after a further 15 s to at least 90% emulsified. 2. Impregnating liquid according to claim 1, characterized in that

• E. Crosslinker to 10 wt .-%, including (meth) acrylic crosslinkers to 6 wt .-%

are limited. 3. impregnating liquid according to claim 1, characterized, that the A / B ratios are between 2.5 and 7. 4. Use of an impregnating liquid according to one of Claims 1-3 in a method of impregnation a porous solid article, in particular one Cast or sintered metal parts, by in in itself well-known way of filling the pores with a polymerizable impregnating liquid, rinsing the solid object after filling the pores with the Impregnating with water and polymerizing the Impregnating fluid in the pores. 5. Use according to claim 4, characterized, that the impregnating liquid prior to introduction into the Pores with a free radical generator and an inhibitor is offset. 6. Use according to one of claims 4 or 5, characterized, that the impregnating liquid contained in the pores by immersing the solid object in water one Temperature 70 ° C is polymerized.