EP0301120B1 - Cold metal forming lubricant and method for its manufacture - Google Patents

Abstract

The invention relates to a liquid lubricant for cold-forming and to a process for producing it. The lubricant contains, in water, one or more fatty acid salts as lubricant and 0.2 to 1.8 % by mass of polyvinyl alcohol and/or 0.2 to 3 % by mass of a polyvinyl alcohol which has been structurally modified with an oxidising agent and which contains, in addition to its hydroxyl groups determining the structure, keto groups and carboxyl groups and/or carboxylate ion groups and can also contain aldehyde groups and/or olefin groups conjugated with keto groups. In addition to 1 to 45 % by mass of water-insoluble fatty acid salts, of which >/= 65 % have a chain length of >/= 16 C atoms, the lubricant also contains 0 to 1.5 % by mass of water-soluble alkali metal soaps, 1 to 6 % by mass of glass-forming borates and/or boric acid esters of the two types of polyvinyl alcohols and 0 to 1 % by mass of surfactants. For producing it, a concentrate is prepared from polyvinyl alcohol and water and the structure of the polyvinyl alcohol is at least partially modified therein by means of an oxidising agent. This concentrate and also fatty acid salts and, if required, surfactants are then introduced into water. Finally, the glass-forming borates or boric acid esters are added.

Description

The invention relates to a liquid lubricant for the cold forming of metallic materials and its production, which is used, for example, in cold rolling, cold upsetting, thread rolling, drawing sheet metal parts, calibrating sintered bodies, stranding and bending, and in particular when drawing strand-like shaped material such as wire, profiles and Pipes, is advantageously applicable.

When pulling wires, profiles, pipes, etc. a lubricant must be applied to the drawing material before the drawing tool, which is to prevent direct contact between the working surfaces of the drawing tool and the surface of the drawing material. The use of solid, semi-solid or liquid lubricants at room temperature is common.

The liquid lubricants used include Oils, chlorinated paraffins, soap solutions and reactive fatty acid soaps are used in conjunction with a basic chemical coating. Liquid lubricants are also known which consist of solid lubricants dispersed in water. In one of these lubricants, alkaline earth metal soaps are used as solid lubricants. The lubricant also contains 2% by mass of polyvinyl alcohol as a dispersant for the solid lubricant, a corrosion inhibitor and surface-active substances. The lubricant is applied to the material to be formed, for example in the immersion process, and then dried, a solid lubricant film being produced for the subsequent forming process.

A disadvantage of this lubricant is that the dried solid lubricant film experiences a significant reduction in quality due to the thermal degradation of the polyvinyl alcohol that occurs during the shaping process, in particular with regard to its dynamic viscosity, its temperature resistance and its adhesiveness. Due to this reduction in quality, large cross-sectional reductions per train or only small total cross-sectional decreases per lubricant application are possible. In addition, this lubricant allows only low drawing speeds due to thermal degradation, and the forming of difficult-to-form materials is also critical.

0,05 - 10 %

Metallseifen, wie Natriumstearat, Bariumstearat und Calciumstearat,

0,05 - 3 %

grenzflächenaktive Mittel/Tenside,

0,1 - 30 %

Ligninverbindungen, z.B. Thiolignin, Natriumthioligninsulfonat, Calcium-thioligninsulfonat und entsprechende Ammoniumsalze,
und gegebenenfalls

0,1 - 7 %

wasserlösliche Polymere oder Polymeremulsionen, z.B. Polyvinylharze, wie beispielsweise Polyvinylacetat oder Polyacrylate.

FR-A-2 102 283 discloses lubricants for cold forming metallic materials, which in principle contain the following components:

0.05 - 10%

Metal soaps, such as sodium stearate, barium stearate and calcium stearate,

0.05 - 3%

surfactants / surfactants,

0.1 - 30%

Lignin compounds, for example thiolignin, sodium thiolignin sulfonate, calcium thiolignin sulfonate and corresponding ammonium salts,
and if necessary

0.1 - 7%

water-soluble polymers or polymer emulsions, for example polyvinyl resins, such as polyvinyl acetate or polyacrylates.

In addition, these lubricants may also contain inorganic water-soluble salts, such as fatty acid salts, alkali phosphates, alkali borates and ammonium salts. The lignin compounds contained serve as dispersants and solubilizers for the present metal soaps.

10 - 50

Masseteile eines wasserlöslichen thermoplastischen Kunstharzes, z.B. Polyvinylalkohol, modifizierte Polyvinylalkohole oder Polyacrylate,

40 - 180

Masseteile einer wäßrigen Dispersion einer Erdalkalimetallseife einer Seifenkonzentration von 40 bis 60 %, z.B. von C₈₋₂₂-Fettsäuren,
sowie gegebenenfalls

0,5 - 12

Masseteile Korrosionsinhibitoren, z.B. Ammoniumborate,

wobei dieses Gemisch in der drei- bis sechsfachen Menge Wasser dispergiert wird.DE-A-24 37 877 also shows a surface treatment agent which is intended in particular for deep-drawing metal sheets and has the following basic composition:

10 - 50

Parts by weight of a water-soluble thermoplastic synthetic resin, for example polyvinyl alcohol, modified polyvinyl alcohols or polyacrylates,

40-180

Parts by weight of an aqueous dispersion of an alkaline earth metal soap with a soap concentration of 40 to 60%, for example of C₈₋₂₂ fatty acids,
and if necessary

0.5 - 12

Parts by weight of corrosion inhibitors, for example ammonium borates,

this mixture being dispersed in three to six times the amount of water.

The modified polyvinyl alcohols are, for example, phosphatically esterified or carboxy-modified polyvinyl alcohols, for example the ammonium salts of corresponding phosphate esters or corresponding carboxylates. The alkaline earth metal soap is used as an aqueous dispersion which is prepared by dispersing the soap in water using at least one anion-active compound and / or nonionic surface-active compound.

The invention is based on the object of specifying a liquid lubricant which gives high-performance liquid or solid lubricating coatings on metal material to be formed, and a method for its production. The object is achieved according to claims 1 and 7. The dependent claims relate to advantageous embodiments.

• (A) wasserunlösliche Fettsäuresalze,
• (B) 0 bis 1,5 Masse-% wasserlösliche Alkalimetallseifen,
• (c) glasbildende Borate
  und
• (D) 0 bis 1 Masse-% eines oder mehrerer Tenside;
  es ist
  gekennzeichnet durch
• (E) 0,2 bis 1,8 Masse-% eines oder mehrerer Polyvinylalkohole
  und/oder
• (F) 0,2 bis 3 Masse-% eines mit einem Oxidationsmittel strukturmodifizierten Polyvinylalkohols, der neben den strukturbestimmenden Hydroxylgruppen Ketogruppen, Carboxylgruppen und/oder Carboxylationengruppen enthält und ggfs. Aldehydgruppen und/oder mit Ketogruppen konjugierte Olefingruppe aufweist,
  und
• (G) 1 bis 6 Masse-% Borsäureester der Polyvinylalkohole E und/oder F,

• 1 bis 45 Masse-% der wasserunlöslichen Fettsäuresalze A, von denen ≧ 65 % eine Kettenlänge von ≧ 16 C-Atomen aufweisen,
  und
• 1 bis 6 Masse-% der glasbildenden Borate C.

The lubricant according to the invention contains in water

• (A) water-insoluble fatty acid salts,
• (B) 0 to 1.5% by mass of water-soluble alkali metal soaps,
• (c) glass-forming borates
  and
• (D) 0 to 1% by mass of one or more surfactants;
  it is
  marked by
• (E) 0.2 to 1.8 mass% of one or more polyvinyl alcohols
  and or
• (F) 0.2 to 3% by mass of a polyvinyl alcohol which has been modified with an oxidizing agent and which, in addition to the structure-determining hydroxyl groups, contains keto groups, carboxyl groups and / or Contains carboxylate ion groups and optionally has aldehyde groups and / or olefin groups conjugated with keto groups,
  and
• (G) 1 to 6% by mass of boric acid esters of polyvinyl alcohols E and / or F,

• 1 to 45% by mass of the water-insoluble fatty acid salts A, of which ≧ 65% have a chain length of ≧ 16 carbon atoms,
  and
• 1 to 6% by mass of the glass-forming borates C.

According to the invention, both types of polyvinyl alcohols E and F preferably have a degree of polymerization in the range from 100 to 1500, the total content of polyvinyl alcohols E and F being ≦ 3% by mass if both types are present.

As water-insoluble fatty acid salts A are preferred Alkaline earth metal soaps and preferably technical calcium stearate are present in an amount of 3 to 8% by mass. The water-soluble alkali metal soaps B advantageously contain sodium soaps, preferably technical sodium stearate.

Suitable glass-forming borate C are e.g. Alkali borates and preferably borax.

Suitable surfactants D are in particular anionic and nonionic surfactants and in particular polyethylene oxide adducts, preferably nonylphenol-polyethylene oxide adducts.

• (I) Herstellung eines Konzentrats aus Polyvinylalkohol und Wasser und zumindest teilweise Strukturmodifizierung des Polyvinylalkohols mit einem Oxidationsmittel,
• (II) Einbringen des Konzentrats aus Schritt I sowie der Fettsäuresalze A und B und ggfs. der Tenside D unter Rühren in Wasser
  und
• (III) Zugabe der glasbildenden Borate C bzw. der Borsäureester G.

The process according to the invention for producing this lubricant is characterized by the following essential steps:

• (I) production of a concentrate from polyvinyl alcohol and water and at least partial structural modification of the polyvinyl alcohol with an oxidizing agent,
• (II) Introducing the concentrate from step I and the fatty acid salts A and B and possibly the surfactants D with stirring in water
  and
• (III) addition of glass-forming borates C or boric acid esters G.

According to the invention, hydrogen peroxide, oxygen, ozone, peroxides, peroxo salts, hypochlorites, chlorates, dichromates and / or permanganate can be used as the oxidizing agent. The preferred oxidizing agent is hydrogen peroxide.

According to an expedient embodiment of the method, the oxidizing agent is reacted with an acidic polyvinyl alcohol solution, preferably with a pH of 1.5 to 4. The oxidizing agent can also be reacted with an alkaline polyvinyl alcohol solution, preferably with a pH of 8 to 12.5. According to a further expedient embodiment of the invention, the oxidizing agent is first reacted with an acidic polyvinyl alcohol solution, whereupon the pH is shifted to the alkaline range during the reaction by adding alkali metal hydroxides, preferably sodium hydroxide.

Depending on the composition and application temperature in the liquid state, the lubricant according to the invention has a low to high viscosity and guarantees a high coating mass and a homogeneous and thermally stable lubricant layer on the material to be formed. This enables high individual degrees of forming and forming speeds to be achieved, and the forming of difficult-to-form materials is also possible. In addition, intermediate coatings between individual forming stages can be largely avoided. If the lubricant contains structure-modified polyvinyl alcohol, there is no or only a slight tendency to form skin or gel, which has a particularly favorable effect on the coating and drying effort.

The invention is explained in more detail below on the basis of exemplary embodiments.

example 1

To a 10% aqueous polyvinyl alcohol solution which contains a polyvinyl alcohol which is 2% esterified with acetate groups and which has a pH of 2.2 and a temperature of 93 ° C., 0.03% Hydrogen peroxide added as an oxidizing agent. After a reaction time of 15 minutes, the solution is made alkaline with sodium hydroxide, the oxidation reaction is continued for a further 10 minutes while maintaining the specified temperature, and then an aqueous calcium soap dispersion which contains an alkylphenol-polyethylene oxide adduct as a dispersant is mixed in to prepare a lubricant concentrate. This concentrate is diluted with water before use for cold forming and sodium stearate is added at a temperature of 80 ° C. Finally, borax is added. The ready-to-use lubricant is made from the following composition: (Dimensions-%) Structure modified polyvinyl alcohol 1.8 Calcium soap 6 Alkylphenol polyethylene oxide adduct 0.3 Sodium stearate 1 borax 5 water Rest.

This lubricant is used to coat 6.5 mm thick Mn 6 wire rod in a coil immersion process at 80 ° C. After drying the lubricant, which takes place in a very short time due to the inherent heat of the wire, the wire is removed in 7 steps with a pulling speed of 10 m / s on the 7th block without intermediate coating drawn to a final diameter of 2.0 mm.

Example 2

0.67% hydrogen peroxide at 75 ° C. is added to a 10% strength polyvinyl alcohol solution which contains a polyvinyl alcohol which is 12% esterified with acetate groups and which has a pH of 11.8. After a reaction time of 15 minutes, 0.002% potassium permanganate is added as a catalyst and the oxidation reaction is continued for a further 30 minutes at 75 ° C. A zinc soap dispersion is then mixed with sodium dodecylbenzenesulfonate as the dispersant and then diluted with water. The last component is borax at 75 ° C. The ready-to-use lubricant is made from the following composition: (Dimensions-%) Structure modified polyvinyl alcohol 1.5 Zinc soap 5 Sodium dodecylbenzenesulfonate 0.2 borax 5 water Rest.

This lubricant is used to coat 8.0 mm thick wire rod of 20 Mn B 4 Q quality in a coil immersion process at 75 ° C. After the lubricant has dried, which occurs quickly due to the inherent heat of the wire, the wire is pulled to 7.05 mm in one go. After drawing, the wire has a residual lubricant film that is sufficiently thick for further processing, for example by cold upsetting.

Example 3

To an 8% polyvinyl alcohol solution which contains a polyvinyl alcohol which is 3% esterified with acetate groups and which has a pH of 10.5, 0.2% potassium permanganate in the form of a 4% solution added. After a reaction time of 20 minutes, an aqueous calcium soap dispersion which contains an alkylphenol-polyethylene oxide adduct as a dispersant is mixed in to produce a lubricant concentrate. This concentrate is diluted with water before use to coat wire coils, and sodium metaborate is added as the last component at a temperature of 85 ° C. The finished lubricant is made from the following composition: (Dimensions-%) Structure modified polyvinyl alcohol 1.4 Calcium soap 6 Alkylphenol polyethylene oxide adduct 0.3 Sodium metaborate 4th Manganese dioxide hydrate 0.02 water Rest.

This lubricant is used to coat 5.5 mm thick wire rod of quality 10 Mn Si 6 in a coil immersion process at 85 ° C and to dry it in air. Then the coated wire is drawn in 5 steps without intermediate coating to a final diameter of 2.5 mm.

Example 4

A lubricant is made from the following composition: (Dimensions-%) Calcium stearate 5 Sodium tetraborate decahydrate 5 Polyvinyl alcohol 1.5 water Rest.

The polyvinyl alcohol used is esterified to 12% with acetate groups.

This lubricant is used to coat 6.5 mm thick wire rod of quality C15 in a continuous process. The lubricant layer is then dried and then the wire is drawn to 3.6 mm in 6 steps at a pulling speed of 7 m / s.

Example 5

A lubricant is made from the following composition: (Dimensions-%) Calcium stearate 4th Sodium metaborate 6 Polyvinyl alcohol 1 water Rest.

2.5 mm thick patented steel wire of quality D 45 is then coated with the lubricant.

After coating, the lubricant film is dried and the wire is pulled at a pulling speed of 6 m / s in one go to 2.0 mm in diameter.

Example 6

A lubricant is made from the following composition: (Dimensions-%) Calcium stearate 4th Sodium metaborate 2.5 Polyvinyl alcohol 1 water Rest.

The polyvinyl alcohol used is 2% esterified with acetate groups.

A steel wire of quality C 15 Q with an initial diameter of 3.35 mm is drawn to 3.0 mm in one single step in a wet pass.

Claims (10)

1. A lubricant for the cold forming of metallic materials that contains

   (A) water-insoluble fatty acid salts,

   (B) 0 to 1.5 weight % water-soluble alkali metal soaps,

   (C) glass-forming borates
   and

   (D) 0 to 1 weight % of one or several surfactants,
   characterized by

   (E) 0.2 to 1.8 weight % of one or several polyvinyl alcohols
   and/or

   (F) 0.2 to 3 weight % of a polyvinyl alcohol structurally modified by an oxidant and containing keto groups, carboxyl groups and/or carboxylate ion groups in addition to the structure-determining hydroxyl groups, and optionally having aldehyde groups and/or olefin groups that are conjugated with keto groups,
   and

   (G) 1 to 6 weight % boric acid esters of the polyvinyl alcohols E and/or F,

   - 1 to 45 weight % of the water-insoluble fatty acid salts A, of which ≧ 65 % have a chain length of ≧ 16 C atoms,
   and

   - 1 to 6 weight % of the glass-forming borates C.
2. A lubricant according to claim 1, characterized in that the polyvinyl alcohols E and/or F have a degree of polymerization of 100 to 1500.
3. A lubricant according to Claim 1 or 2, characterized in that if both polyvinyl alcohols E and F are present their total amount is ≦ 3 weight %.
4. A lubricant according to one of Claims 1 to 3,
   characterized by
   3 to 8 weight % of one or several alkaline earth metal soaps, preferably calcium stearate, as water-insoluble fatty acid salts A
   and
   one or several sodium salts, preferably sodium stearate, as water-soluble alkali metal soaps B.
5. A lubricant according to one of Claims 1 to 4, characterized by an alkali borate, preferably borax, as glass-forming borate C.
6. A lubricant according to one of Claims 1 to 5, characterized by anionic or non-ionic surfactants, especially a polyethylene oxide adduct and preferably a nonylphenol-polyethylene oxide adduct as surfactants D.
7. A process for production of the lubricant according to one of Claims 1 to 6,
   characterized by

   (I) production of a concentrate from polyvinyl alcohol and water and at least partial structural modification of the polyvinyl alcohol with an oxidant,

   (II) introduction to water with stirring of the concentrate from step (I) as well as the fatty acid salts A and B and optionally the surfactants D
   and

   (III) addition of the glass-forming borates C or of the boric acid esters G.
8. A process according to Claim 7, characterized by the use of hydrogen peroxide, oxygen, ozone, peroxides, peroxo salts, hypochlorite, chlorate, dichromate and/or permanganate as oxidant in step I.
9. A process according to Claim 7 or 8, characterized in that the oxidant is reacted in step I with an acidified polyvinyl alcohol solution, preferably with a pH value of 1.5 to 4, or with an alkalized polyvinyl alcohol solution, preferably with a pH value of 8 to 12.5.
10. A process according to one of Claims 7 to 9, characterized in that the oxidant is reacted in step I with an acidified polyvinyl alcohol solution and the pH is shifted into the alkaline range during the reaction by addition of alkali hydroxides, preferably of sodium hydroxide.