WO2005097899A1

WO2005097899A1 - Polyalkylene glycols having low inhalation toxicity

Info

Publication number: WO2005097899A1
Application number: PCT/US2005/011496
Authority: WO
Inventors: Philip Miller; Frank Disanti; Toni Lynn Brown
Original assignee: The Lubrizol Corporation
Priority date: 2004-04-05
Filing date: 2005-04-05
Publication date: 2005-10-20

Abstract

Working fluids containing low inhalation toxicity polyalkylene glycol copolymers are disclosed. These working fluids are desirable in an application where the fluid is subject to shear and may generate an airborne mist. These include various metalworking applications including grinding, bending, machining, shaping, etc. Optionally, the metal working fluid may be an oil-in-water emulsion.

Description

TITLE : POLYALKYLENE GL YCOLS HAVING LOW INHALATION TOXICITY The invention relates to ethylene oxide/propylene oxide copolymers which are obtainable by copolymerizing ethylene oxide and propylene oxide with a monohydric alcohol having 1 to 12 carbon atom, the copolymer having an ethylene oxide/propylene oxide weight ratio of from 20:80 to 80:20 and a molecular weight of from 1000 to 5000 g/mol, and to their use in lubricant formulations, formulations for fiber preparation and metal machining fluids. BACKGROUND OF THE INVENTION Aqueous metal working fluids comprising of water and an ethylene oxide- propylene oxide copolymer are known. Optionally, the fluid may be an oil-in-water emulsion. Such emulsions include oil and an emulsifier. h addition to the metal working fluid, metal cutting operations involve a work piece and a cutting tool, either of which rotates or otherwise moves at relatively high speed, and both of which are lubricated by a metalworking fluid. Under these conditions, the metalworking fluid is frequently thrown from the surface of the metal in the form of droplets. Often the droplets are small enough to be classified as a mist or aerosol. Misting, or the formation of a mist is considered undesirable, because it represents a loss of the cutting fluid, and the cutting fluid mist is considered a contaminant in the air around the cutting machine. Many of the desirable ethylene oxide-propylene oxide copolymers when suspended as airborne mist are toxic at relatively low concentrations (<5 mg/L when suspended as mist in air) in inhalation studies using rats. It would be desirable to identify a subset of ethylene oxide-propylene oxide copolymers having the necessary lubricious properties, sufficient solubility in water and in water containing metalworking formulations, and being less toxic in inhalation studies.

SUMMARY OF INVENTION Block ethylene oxide-propylene oxide copolymers having up to 5 blocks, initiated with monohydric alcohols such that one ether terminus is created, and having a molecular weight from about 1000 to 5000 were found to have inhalation toxicity^ at LC 50 for 4 hours using rats of greater than 5 mg/L. These particular copolymers are also suitable for use in working fluids in open systems where the fluids can be sheared into an airborne mist.

DETAILED DESCRIPTION OF THE INVENTION [0002] The present invention relates to polyalkylene glycol copolymers which are used as base oils for water-soluble lubricant formulations, and to their use in open systems which tend to form aerosols. The preferred polyalkylene glycols (also mown as poly(alkylene oxide)) are blocky in nature (indicated by a predominance of repeating units from a first monomer in one portion of the polymer and a predominance of a repeating units from a second (different) monomer in a subsequent block). A preferred number of blocks is between two and five with two and four blocks being preferred. A preferred initiator is a monohydric aliphatic or cycloaliphatic alcohol having from 1 to 12 carbon atoms with 3 to 8 carbon atoms being more desirable and 3-5 carbon atoms being most desirable. This type of initiator is known to form polymers with about one ether terminus per molecule under conventional polymerization schemes where the other terminus is usually a hydrox;yl group. Preferred number average molecular weights are from about 1000 to 500O grams/mole with a more preferred range being from about 1000 to 3000 grams/rnole. [0003] Random copolymers with ethylene oxide and propylene oxide as starting monomers have been used for many years as base oils and as additives for the preparation of high-performance lubricants whose major areas of application are the production of metal machining fluids and lubricants in fiber processing. This group of products is synthetically obtainable by anionic polymerization of ethylene oxide together with propylene oxide, starting from a mono- or polyfunctional alcohol ate. [0005] The major advantages of these polyglycol random copolymers as lubricants are their high viscosity index (i.e. low temperature dependence of the viscosity), low coefficients of friction even without the addition of friction/antiwear additives, controlled establishment of tfcie degree of water solubility of the copolymer through the choice of the ethylene oxide/propylene oxide ratio (which significantly influences the cloud point) and very low pour points. Linear copolymers having a weight ratio of ethylene oxide to propylene oxide monomers in the range from 40:60 to 60:40 have proven particularly advantageous. These copolymers have, on the one hand, very low pour points of less than -30 degree °C, good water solubility (cloud points greater than 50 degrees °C) and very high viscosity indexes (greater than 250). [0006] Recently, however, toxicological studies of aerosols of this class of substances have shown that these products are potentially very hazardous to health. (Literature: ECETOC, European Centre for Ecotoxicology and Toxicology of Chemicals, Technical Report No. 55, March 1997). Thus, for example, monobutoxyethylene oxide/propylene oxide copolymers which contain ethylene oxide and propylene oxide in a weight ratio of 50:50 exhibited, at a molecular weight of about 4000 g/mol, very high aerosol toxicity characterized by a low LC 50 value of only 106 mg/m³ (0.106 mg/L). Furthermore, pure ethylene oxide/propylene oxide random copolymers which contain ethylene oxide and propylene oxide in a weight ratio of 50:50 and have a molecular weight of 4000 g/mol showed LC50 values of about 300 mg/m³ (D. B. Warheit, Inhalation Toxicol. (1995), 7 (3) 377- 92). This high toxicity of the aerosol made it necessary for processors and users of these linear copolymers to take complicated technical measures, such as, for example, encapsulation of the plants, for protecting the personnel from aerosols. [0007] It was accordingly the object of the present invention to prepare base oils and additives for lubricants, which oils have good water solubility and similarly high viscosity indexes and low coefficients of friction as the ethylene oxide/propylene oxide copolymers obtainable from monofunctional alcoholates and which have low pour points and low cloud points so as to provide lubrication on softer metals, for example, aluminum and its alloys. However, these base oils and additives should have no toxicological potential on aerosol formation and should thus dispense with complicated protective measures during handling. [0008] Surprisingly, it was found that monohydric alcohol initiated block ethylene oxide/propylene oxide copolymers having at least one ethylene oxide (EO) and at least one propylene oxide (PO) block and having a weight ratio of EO to PO from 20:80 to 80:20, have outstanding properties with regard to pour point, water solubility, formulation stability, cloud points in the 25 to 45 degree C range so as to provide sufficient lubrication on soft metals such as aluminum and its alloys, and a high viscosity index and at the same time are not toxic on exposure to aerosols. This makes it possible, especially when they are used in the formulation of aqueous metal machining fluids, to avoid complicated technical measures for encapsulating the plants for protection from exposure. [0009] The invention therefore relates to ethylene oxide/propylene oxide copolymers which are obtainable by copolymerization of ethylene oxide and propylene oxide with a monohydric alcohol having 1 to 12 carbon atoms, the copolymer having an ethylene oxide/propylene oxide weight ratio of from 20:80 to 80:20 and a molecular weight of from 1000 to 5000 g/mol. [0010] The invention furthermore relates to the use of the copolymers according to the invention for lubricant formulations, formulations for fiber preparation and metal machining fluids, preferably in open systems. Here, open systems are understood as meaning apparatuses in which lubricant formulations, formulations for fiber preparation and metal machining fluids are used and in which aerosols form which may pass from these apparatuses to the outside. [0011] The invention furthennore relates to lubricant formulations, formulations for fiber preparation and metal machining fluids which contain the copolymers according to the invention. [0012] The use of glycols in lubricants and glycol-containing lubricant formulations are described in W. J. Barz, Tribologie und Schmierungstechnik [Tribology and Lubrication Technology], Part 5 (1987), pages 262 to 269. The use of glycols in fiber preparation compositions and glycol-containing fiber preparation compositions are described in P. Ehrler, Textilveredelung [Textile Finishing], Part 16 (1981), pages 403 to 414 and in R. S. Jinkins, K. K. Leonas, 1994 Student Paper Competition, Part 12 (1994), pages 25 to 29. The use of glycols in metal machining fluids and glycol-containing metal machining fluids are described in W. L. Brown, Lubrication Engineering, 1988, pages 168 to 171. The disclosure of these documents is hereby incorporated. [0013] Preferred copolymers according to the invention have a viscosity at 40 degrees C. of from 50 to 1000 mmVs, determined according to DIN 51562. A viscosity index greater than 200 to 350, determined according to ASTM D2270-93, is likewise preferred. In a further preferred embodiment, the copolymers have a pour point, determined according to ISO 301 , of less than 10 degrees C. A hydroxyl number of from 10 to 60 mg KOH/g is preferred. [0014] Depending on the monohydric alcohol, the ratio of ethylene oxide to propylene oxide is preferably chosen so that the copolymers according to the invention have a 1 wt.% (solution in water) cloud point of from 25 to 45 or 50 degrees C. [0015] The copolymers according to the invention are prepared by sequentially reacting ethylene oxide and propylene oxide with a monohydric alcohol. The copolymers are generally characterized by the formula

RO-(EO)_w-(PO)_z-H or RO-(EO)_w-(PO)_x-(EO)_y-(PO)_z-H [0016] in which R= an aliphatic alkyl or cylcoalkyl group with 1 to 12 carbon atoms which may also be branched, and w, x, y, and z are integers between 4 and 50 and (w + x + y + z) is less than or equal to 120. hi the sequential reaction/polymerization of ethylene oxide and propylene oxide there may be a small portion of random copolymerization of ethylene oxide and propylene oxide, but the preferred reaction is sequential homopolymerization of either ethylene oxide or propylene oxide. The terminus of the growing chain can be a hydroxyl group or the polymer could be end capped as is well known to the art of anionic polymerization of alkylene glycols. A preferred composition includes a terminal hydroxyl group. [0017] Preferred alcohols for the preparation of the copolymers according to the invention are methanol, ethanol, propanol, butanol, pentanol, hexanol, blends thereof etc. [0018] For this purpose, the corresponding monohydric alcohol(s) are added to a pressure-resistant reactor and, after the addition off the catalyst for forming the corresponding alcoholates (usually potassium hydroxide or potassium methylate), are reacted under pressure sequentially in any order with ethylene oxide and thereafter propylene oxide and so on in the desired amount while stirring in an anionic polymerization. The resulting polymer is neutralized by adding acid. While alkali catalysis is traditionally the preferred mechanism to add ethylene oxide and/or propylene oxide to an alcohol initiator, other catalysts may be employed to accomplish the desired composition. The desired visco sity is determined by means of the resulting molecular weight and from the ratio of^" monohydric alcohol to total ethylene oxide and propylene oxide. [0019] Typical formulations for lubricants can contain, other than water and in addition to polyalkylene glycol as the main component, antiwear additives, EP

(extreme pressure) additives, antioxidants, corrosion inhibitors, reserve alkalinity agents (for example alkanolamines) and antifoams (cf. for example EP-A-0 402

009). [0020] The copolymers according to the invention have a very low aerosol toxicity, determined according to independent toxicolological testing laboratories of in general more than 5000, in particular more than 400O, especially more than 3000, mg/m³. They are therefore particularly suitable for use in those processes in which copolymers occur in the form of a fine mist/aerosol. [0021] The invention is to be explained in more detail with reference to a few examples. Example 1 [0022] Butanol-initiated ethylene oxide/propylene oxide copolymer, [0023] MW 1600 g/mol [0024] 4.3 moles of butanol is reacted with 0.2 moles of sodium methanolate in a laboratory autoclave to give the alcoholate. Methanol is distilled off under reduced pressure. The vacuum is replaced with nitrogen-. Thereafter, 10.5 moles of ethylene oxide is added at a rate to maintain the temperature between 120 and 130 degrees C. The pressure is maintained below 70 psi. After all is added, the mixture is heated for an additional half hour. The hydroxyl no. is 109, indicating a molecular weight of 515. To 1.05 moles of the first intermediate is added 6.73 moles of propylene oxide at 110 - 120 degrees C. and a pressure b elow 70 psi After all is added, the mixture is heated for an additional half hour. Ttie hydroxyl no. is 65.1, indicating a molecular weight of 862. To 0.95 moles of the second intermedia.te is added 10.1 moles of ethylene oxide at 110 - 120 degrees C. and a pressure b elow 70 psi After all is added, the mixture is heated for an additional 45 minutes. The hydroxyl no. is 43.1, indicating a molecular weight of 1302. To 0.94 moles of the third intermediate is added 12.6 moles of propylene oxide at 110 - 120 degrees C. and a pressure below 70 psi. After all is added, the mixture is heated for an additional 16 hours. Tlie hydroxyl no. is 34.9 indicating a molecular weight of 1607. The cloud point at this point is 48.5 degrees C. Addition of another 2.6 moles of propylene oxide at 110 - 120 degrees C. followed by heating for an additional 2 hours afforded a product having a hydroxyl no. of 35.1 corresponding to a molecular weigh-t of 1598. The cloud point is 44.5 degrees C. The product is neutralized with acetic acid to give a 1 % aqueous pH of 6.7. Example 2 [0026] Butanol-initiated ethylene oxide/propylene oxide copolymer, [0027] MW 1540 g/mol [0028] 4.3 moles of butanol is reacted w ith 0.3 mol of sodium methanolate in a laboratory autoclave to give the alcoholate. Methanol is distilled off under reduced pressure. The vacuum is replaced with nitrogen. Thereafter, 10.8 moles of ethylene oxide is added at a rate to maintain the temperature between 120 and 130 degrees C. The pressure is maintained below 70 psi. After all is added, the mixture is heated for an additional half hour. The hydroxyl no. is 101.9, indicating a molecular weight of 550. To 0.73 moles of the first intermediate is added 4.7 moles of propylene oxide at 120 - 130 degrees C and a pressure below 70 psi After all is added, the mixture is heated for an additional 2 1/2 hours. The hydroxyl no. is 65.4, indicating a molecular weight of 858. To 0.75 moles of the second intermediate is added 7.5 moles of ethylene oxide at 120 - 130 degrees C and a pressure below 70 psi. After all is added, the mixture is heated for an additional hour. The hydroxyl no. is 44.2 indicating a molecular weight of 1269. To 0.74 moles of the third intermediate is added 18.6 moles of propylene oxide at 120 - 130 degrees C and a pressure below 70 psi. After all is added, the mixture is heated for an additional 16 hrs. The hydroxyl no. is 36.5 indicating a molecular weight of 1537. The cloud point is 40 degrees C. The product is neutralized with acetic acid to give a 1% aqueous pH of 7.6. Example 3 Butanol-initiated ethylene oxide/propylene oxide copolymer, [0027] MW 1731 g/mol [0028] 4.3 moles of butanol is reacted with 0.3 mol of sodium methanolate in a laboratory autoclave to give the alcoholate. Methanol is distilled off under reduced pressure. The vacuum is replaced with nitrogen. Thereafter, 11.6 moles of ethylene oxide is added at a rate to maintain the temperature between 120 and 130 degrees C. The pressure is maintained below 70 psi. After all is added, the mixture is heated for an additional half hour. The hydroxyl no. is 91.0, indicating a molecular weight of 616. To 0.56 moles of the first intermediate is added 4.0 moles of propylene oxide at 120 - 130 degrees C. and a pressure below 70 psi After all is added, the mixture is heated for an additional 3 hours. The hydroxyl no. is 54.4, indicating a molecular weight of 1031.. To 0.44 moles of the second intermediate is added 5.3 moles of ethylene oxide at 120 - 130 degrees C. and a pressure below 70 psi. After all is added, the mixture is heated for an additional hour. The hydroxyl no. is 36.1 indicating a molecular weight of 1554. To 0.37 moles of the third intermediate is added 6.17 moles of propylene oxide at 120 — 130 degrees C. and a pressure below 70 psi. After all is added, the mixture is heated for an additional 16 hrs. The hydroxyl no. is 32.4 indicating a molecular weight of 1731. The cloud point is 39.5 degrees C. The product is neutralized with acetic acid to give a 1 % aqueous pH of 6.1.

In the investigation of the aerosol toxicity on rats, as described in Example 3, the copolymer has an LC50 value greater than 5630 mg/m³ . The copolymer is thus outstandingly suitable for the formulation of lubricants an-d metal machining fluids which are used in open systems. Example 4 [0030] Gear lubricant could be prepared from the polyglycol from Example 3 as explained below. [0031] 0.5% by weight of monoisotridecyl phosphate, 0.05% by weight of benzotriazole, 0.5% by weight of butylhydroxyanisole, 0.5% by weight of 4,4'- methylenebis-2,6-di-tert-butylphenol and 2% by weight of phenyl-alpha- naphthylamine could be stirred into 96.45% by weight of the polyglycol from Example 2 at 80 degree °C. The resulting oil would be outstanding for use as a high- viscosity gear oil. Example 5 [0032] Fiber lubricant could be prepared from the polyglycol from Example

3 as explained below. [0033] 5% by weight of Genapol LA 070 (fatty alcohol ethoxylate) and 0.5% by weight of butylhydroxyanisole and 1.5% by weight of lauryldimethylamine oxide could be stirred into 93% by weight of the polyglycol from Example 2 at 80 degree °C. The resulting oil would be outstandingly suitable as an excellent lubricant in fiber production, without further additives. Comparative Example [0034] Methanol-initiated ethylene oxide/propylene oxide copolymer [0035] 0.1 mol of sodium methanolate dissolved in methanol is reacted in a laboratory autoclave to give the alcoholate. Methanol is distilled off under reduced pressure. Thereafter, a mixture of 15 mol of ethylene oxide and 15 mol of propylene oxide is added and polymerization is carried out for 1 0 hours at about 140 degrees C under pressure. The resulting polymer is neutralized with lactic acid. The characteristics are determined as described in Example 1. The hydroxyl number is 11 mg KOH/g. According to the hydroxyl number, it has a molecular weight of about 5000 g/mol. The viscosity is 690 mm²/s at 50 degrees °C, the viscosity index is 280, the pour point is -35 degrees C and the cloud point in water is 49 degrees C. [0036] However, on investigation of the aerosol toxicity on rats, the copolymer has an LC.50 value of 100 mg/m³ (or 0.10 mg/L). The linear copolymer is therefore to be regarded as toxic on inhalation and is not suitable for formulating lubricants and metal machining fluids which are used in open systems.

Inhalation Toxicity Results

Example 6. Various random and block polyglycols were formulated in very concentrated mixtures to enable predicting their stability in synthetic metalworking formulations. The following data was generated by weighing 14.0 grams of triethanolamine, 6.6 grams of heptanoic acid, and varying the water and polyglycol content per the table below to a total of 100 grams: Formulation Stability Results

In addition to the alkylene glycol polymer, the aqueous metal working fluids may contain additives to improve the properties of the composition. These additives include anti-foam agents, metal deactivators, and corrosion inhibitors, antimicrobial, anticorrosion, extreme pressure, antiwear., antifriction, antimist agents such as AMPS containing copolymers sold by The Lubrizol Corporation, and antirust agents. Such materials are well known to th-ose skilled in the art. The metal working fluids of the present invention may also be oil-in-water emulsions. The emulsion compositions contain the same types and amounts of alkylene glycol polymers as the purely aqueous compositions discussed above. The compositions may also contain the property improving additives which have been used in the purely aqueous fluids noted above. The oils used in the optional emulsion compositions may include petroleum oils, such as oils of lubricating viscosity, crude oils, diesel oils, mineral seal oils, kerosenes, fuel oils, white oils, and aromatic oils. Liquid oils include natural lubricating oils, such as animal oils, vegetable oils, mineral lubricating oils, solvent or acid treated mineral oils, oils derived from coal or shale, and synthetic oils. Synthetic oils include hydrocarbon oils and halo-substituted hydrocarbon oils such as polymerized and interpolymerized olefins, for example polybutylenes, polypropylenes, propylene-isobutylene copolymers, chlorinated polybutylenes, poly(l-hexenes), poly(l-octenes), poly(l-decenes); alkyl benzenes, such as dodecylbenzenes, tetradecylbenzenes, dinooylbenzenes, di-(2-ethylhexyl)benzenes; polyphenyls such as biphenyls, terphenyls, and alkylated polyphenyls; and alkylated diphenyl ethers and alkylated diphenyl sxilfides and derivatives , analogs and homologs thereof. Alkylene oxide polymers and derivatives thereof where terminal hydroxy groups have been modified by esterification, etherification etc. constitute another class of synthetic oils. These are exemplified by polyoxyalkylene polymers prepared by the polymerization of ethylene oxide or propylene oxide, the alkyl and aryl ethers of these polyoxyalkylene polymers such as methyl-polyisopropylene glycol ethers, diphenyl and diethyl ethers of polyethylene glycol; and mono and polycarboxylic esters thereof, for example, the acetic esters, mixed C₃ - C₈, fatty acid esters and ₃ OxO diester of tetraethylene glycol. Simple aliphatic ethers may be used as synthetic oils, such as, dioctyl ether, di ecyl ether, di(2-ethylhexyl) ether. Another suitable class of synthetic oils comprises the esters of fatty acids such as ethyl oleate, lauryl hexanoate, and decyl palmitate. The esters of dicarboxylic acids such as phthalic acid, succinic acid, maleic acid, azelaic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acids, alkenyl malonic acids with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoethyl ether, and propylene glycol. Specific examples of these esters include dibutyl adipate, di(2-ethylhex;yl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisoctyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, and the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethyl-hexanoic acid. Any oil-in-water emulsifier may be used to prepare the emulsions of the present invention. Emulsifiers may be single materials or may be mixtures of surfactants. Typical emulsifiers include alkali metal sulfonates and carboxylates, salts derived from the reaction product of carboxylic acylating agents with amines and hydroxylamines, polyols, polyether glycols, polyethers, and polyesters and the like. The Kirk-Othmer Encylopedia of Chemical Technology (3rd. Edition N. 8 pp. 900 - 930) provides a good discussion of emulsions and provides a list of emulsifiers useful in preparation of oil-in-water emulsions. A typical metal working fluid would include other components such as anti- foam agents, metal deactivators, corrosion inhibitors, antimicrobial, extreme pressure, antiwear, antifriction, and antirust agents. Typical anti-friction agents include overbased sulfonates, sulfurized olefms, chlorinated paraffins and olefms, sulfurized ester olefms, amine terminated polyglycols, and sodium dioctyl phosphate salts. Useful anti-foam agents include: alkyl polymethacrylates, and polymethylsiloxanes. Metal deactivators include materials such as tolyltriazoles. Corrosion inhibitors include carboxylic/boric acid diamine salts, carboxylic acid amine salts, alkanol amines, alkanol amine borates and the like.

Claims

1. A method for lubricating a metal work piece in a metal removal or metal deformation operation, comprising: supplying to said work piece a composition comprising (a) water and (b) a copolymer formed by sequentially polymerizing segments of ethylene oxide and propylene oxide onto a monohydric alcohol having from 1 to 13 carbon atoms to form a block ethylene oxide-propylene oxide copolymer having two to five blocks and a number average molecular weight from about 1000 to about 5000 gram/mole.

2. A method according to claim 1, wherein said copolymer has a cloud point for a 1% solution in water of from 25 °C to about 50°C.

3. A method according to claim 2, wherein the molecular weight is from about 1000 to about 3000.

4. A method according to claim 2, wherein the monohydric alcohol comprises butanol.

5. A process for open lubrication of a metal or a fiber comprising contacting the metal or the fiber with an ethylene oxide/propylene oxide copolymer which is obtainable by sequentially polymerizing ethylene oxide and propylene oxide with an initiator monohydric alcohol having 1 to 12 carbon atoms, the copolymer having a viscosity from 50 to 1000 mm²/s at 40 degrees °C, a viscosity index of more than 200, an ethylene oxide/propylene oxide weight ratio of from 20:80 to 80:20 and a molecular weight of from 1O00 to 5000 g/mol.

6. The process of claim 5, wherein said copolymer has a cloud point for a 1 % solution in water of from 25 °C to about 50°C .

7. A process for open lubrication of metal comprising applying to the metal an aqueous lubricant comprising an ethylene oxide/propylene oxide copolymer which is obtainable by sequentially polymerizing ethylene oxide and propylene oxide with a monohydric alcohol initiator having 1 to 12 carbon atoms, the copolymer having an ethylene oxide/propylene oxide weight ratio of from 20:80 to 80:20 and a molecular weight of from 1000 to 5000 g/mol and said ethylene oxide/propylene oxide copolymer having an aerosol toxicity of more than 5000 mg/m³.

8. A process for open lubrication of fiber comprising applying to the fiber an aqueous lubricant comprising an ethylene oxide/propylene oxide copolymer which is obtainable by sequentially polymerizing ethylene oxide and propylene oxide with a monohydric alcohol initiator having 1 to 12 carbon atoms, the copolymer having an ethylene oxide/propylene oxide weight ratio of from 20:80 to 80:20 and a molecular weight of from 1000 to 5000 g/mol and said ethylene oxide/propylene oxide copolymer having an aerosol toxicity of more than 5000 mg/m³.