BACKGROUND OF THE INVENTION

l - Field of the Invention

This invention relates to copolymers of tetrahydrofuran (THF) and ethylene oxide (EO) , and, more particularly, to liquid surfactant polymers of THF and EO having a vide range of molecular weight and monomer content.

2. Description of the Prior Art

Surfactants based upon copolymers of THF and EO are disclosed as alternatives to nonionic surfactants. Block copolymers of these monomers have a well-defined hydrophilic and hydrophobic structure and exhibit useful surface active properties. Unfortunately, block copolymers are pastes or solids at ambient temperatures which makes them very difficult to handle.

Kuwamura et al., in the J. of Am. Oil Chem. Soc. 51, 29-34 (Feb., 1971), described block copolymers of ethylene oxide and polyoxytetramethylene glycolβ prepared by cationic polymerization of tetrahydrofuran as being solids with surfactant properties albeit with rather high pour points and poor defoa ing action.

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Grief et al., in U.S. Patent 4,038,296, described modified block copolymers of THF and EO which included a long chain (C ₈ -C ₂₁ ) alcohol. Their product was defined as R-X in which the hydrophobic portion, R, was provided by the long chain hydrocarbon radical of the alcohol, and the hydrophilic end, X, was provided by the reaction product of the THF and EO monomers. These copolymers were disclosed to be useful as textile auxiliaries and surfactants.

Random copolymers of THF and EO, on the other hand, are liquids, but they do not exhibit the effective surface active properties which are characteristic of the corresponding block copolymers. Random copolymers of THF and EO are produced by copoly erizing a mixture of the monomers, or by adding one monomer to the other at a substantially constant feed rate.

Pruckmayr, in U.S. Patent 4,139,567, for example, described the preparation of random copolymers of THF and EO using acidic resins as catalysts for the polymerization. The disclosed process involved precharging THF and the resin catalyst and then slowly bubbling in gaseous EO at a substantially constant feed rate over a two-hour period while holding the reaction mixture at 25*c.

Langdon βt al., in U.S. Patent 4,183,821, disclosed random-block copolymers of THF and EO which were prepared by a two-stage process. The first stage of the process comprised forming the random hydrophobic portion of the polymer by reacting a mixture of THF and SO in the presence of a Lewis acid catalyst. The hydrophobic segment then was capped with a hydrophilic block of ethylene oxide units by a base-catalyzed reaction with £0. The product was a random-block copolymer characterised by an abrupt break between its hydrophobic segment and its hydrophilic cap. Dβmulβifying properties were observed for such polymers but it was not apparent that they had effective surfactant properties.

Knopf et al., in U.S. Patent 4,195,167, disclosed the formation of gradient copolymers of ethylene oxide and propylene oxide which were considered as intermediate between block and random copolymers. Such gradient copolymers of ethylene oxide and propylene oxide were produced by a process in which one of the premixed concentrations of the primary and secondary polymerizable monomer feed compositions was continuously changed during the polymerization. However, a suitable process for preparing liquid copolymers of tetrahydrofuran and ethylene oxide having effective surfactant properties was not disclosed.

The following references are also of interest in this field: U.S. Patents: 3,133,095; 3,194,772; 3,254,056; 3,344,088; 3,359,332; 3,425,999; 3,644,567; 3,834,935; 4,065,520; 4,118,326; 4,198,464; 4,259,405; and 4,299,993; Brit. Pat. No. 854,958; Japan Patent Announcement No. 213-1977; and an article by Murbach, W. and λdicoff, A. in Ind. £ Eng. Chem. , 52, 7725 (1960).

None of the above cited references, however, disclose, describe or suggest a suitable method for preparing copolymers of THF and EO which are liquids at ambient temperatures, and which exhibit effective surfactant properties, i.e. surface tension reduction, low pour points, good defoaming action, and effective lubricity, and wherein such copolymers exhibit these advantageous surfactant properties over a wide range of molecular weights and monomer content.

Accordingly, an object of the invention is to provide liquid surfactant polymers of THF and EO which are effective surfactants over a wide molecular weight range, and, particularly, which exhibit substantial surface tension reduction, low foaming, low pour points, and useful lubricity surfactant properties.

Another object of the invention is to provide a process for making such liquid surfactant polymers.

These and other objects and features of the invention will be made apparent from the following summary and description of the invention.

SUMMARY OF THE INVENTION

The present invention provides a liquid surfactant polymer product which is substantially a copolymer of THF and EO monomers (mer) units. The polymer structure comprises:

(1) a hydrophobic central THF-EO copolymer segment containing predominately THF mer units,

(2) transition THF-EO copolymer segments extending outwardly from the central copolymer segment characterized by a continuously increasing EO mer unit content relative to the THF mer units therein, and

(3) hydrophilic termini polymer segments of substantially £0 mer units.

The liquid surfactant polymers of the invention have useful surfactant properties, including surface tension reduction, low foaming, low pour points, and effective lubricity, within a polymer molecular weight range of about 500 to 10,000, and, preferably, about 1,500 to 5,000.

The invention also provides a multi-stage process for making the liquid surfactant polymer product described herein. In this process, predetermined amounts of EO are added successively to a charge of THF at selected rates. Polymerization is carried out in a predetermined manner at the various stages of the process to form the desired segments of the polymer.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a graphical illustration of the process of the invention, shoving the rate of addition of EO to a charge of THF at each stage of the process.

DETAILED DESCRIPTION OF THE INVENTION

As illustrated in the FIGURE, a 3-stage process is provided for preparing the liquid surfactant polymer product of the invention. During the several stages of the process, three segments of the polymer are provided, each with a predetermined monomer content.

CHARGE

The process is carried out by first charging a reactor with THF monomer reactant and a small amount of a starter compound for the polymerization. The starter will enable linear polymerization of the monomers in one or more directions, depending upon the number of reactive hydrogens in the starter. Suitably, the starter is added in an amount of about 0.1-10 mol % of all monomers present in the reaction. Representative starter compounds include

monohydric or polyhydric alcohols, alcohol, such as butanol, ethylene glycol, butanediol, decanediol , glycerol, pentaerythritol, bis-phenol A, nonyl phenol, polyethylene glycol, polypropylene glycol, polytetrahydrofuran, and the like, and monobasic and polybasic acids, such as acetic acid, stearic acid, succinic acid, oxalic acid, gluaric acid, benzoic acid, and the like, although others known in the art may be used as well, including primary and secondary amines, hydroxyl amines, and water. The reactor is then sealed, purged with nitrogen, and warmed to a reaction temperature. Suitably, the reaction temperature is set above the boiling point of EO (10*C.) and below about 80*C, preferably about 45*-60*C. A polymerization catalyst then is added, such as a Lewis acid, of which BF ₃ -etherate is one example.

HYDROPHOBIC CENTRAL SEGMENT

The EO monomer reactant then is introduced slowly into the charged reactor at a low EO pressure, as shown by stage A in the FIGURE. Suitably, the EO pressure does not exceed about 2 psig, and preferably less than 1 psig. During introduction of the EO monomer, in this stage of the process, the reaction temperature gradually increases, generally, from about 45*C. to about 50*-60 ^β C. Copolymerization is thereby effected between the charged THF reactant and the small amount of added EO to form the hydrophobic central segment of the polymer which contains predominately THF mer units. The EO addition is continued until about 1/2 to 2/3 of the THF charge is consumed. This segment preferably includes, relatively, about 10-20 THF mer units to about 2-4 EO mer units.

TRANSITION COPOLYMER SEGMENTS

Substantially all of the remaining THF reactant then is copolymerized with newly added EO, in stage B, to form the transition THF-EO copolymer segments of the polymer which extend outwardly from the central copolymer segment. These transition segments are characterized by a continuously increasing EO mer unit content relative to the THF mer units therein.

To form the transition segments, the rate of EO addition is increased slowly, for example, up to about 5-8 psig. , over a period of about an hour, as shown in the graph. The EO addition during this stage may be carried out in one step, shown as step B', or, in two successive steps, B ¹ ' and B'''. In the latter pathways, the EO reaction pressure is increased to the desired level (during step B ¹ ') and then it is held constant (during step B''') for a given period of time at the reaction temperature. At the conclusion of stage B, substantially all of the remaining THF charge is consumed to provide the transition segments. Generally, the transition segments preferably include, relatively, about 4-15 THF mer units to about 4-30 EO mer units. The EO mer unit content in these segments continuously increase outwardly and away from the central segment.

HYDROPHILIC TERMINI SEGMENTS

Upon determination by analysis that substantially all the THF charge has been consumed in stage B, the transition segments then are capped with hydrophilic EO polymer termini segments during stage C of the process. These caps are provided by feeding EO into the reactor at an increased rate. Generally, stage C also is carried out in two steps, namely, step C, in which the EO pressure is

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increased substantially, e.g. to about 20 psig, and step C', wherein the remainder of the EO reactant is added. The termini segments preferably contain about 3-40 EO mer units, although lower and higher amounts also may be present.

ISOLATION OF PRODUCT

The reactor then is purged with nitrogen, cooled, e.g. to about 35*C, and the reaction product is discharged. The reaction then is terminated by complexing the catalyst for example, with a diatomaceous earth or by ion-exchange. The reaction product mixture then is stirred, filtered and vacuum stripped of volatiles. The polymer product obtained thereby is a clear, colorless viscous liquid, containing, relatively, about 14-35 THF mer units to about 9-100 EO mer units.

The molecular weight of the polymer product suitably is about 500 to about 10,000, and preferably about 1,500 to 5,000. The product exhibits excellent surfactant properties of substantial surface tension reduction, low foaming, low pour points, and effective lubricity.

The invention will now be described by reference to the following examples.

EXAMPLE 1

λ dry, stainless steel reactor was charged with 256 g. (2.85 moles) of butanediol and 8,616 g. (119 moles) of THF (maximum water content of 0.01%). The reactor was sealed, purged with nitrogen and warmed to 45*C. Then a solution of 10 g. of boron trifluoride-etherate in 15 ml. of diethyl ether was added.

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Ethylene oxide (3,258 g. , 74 moles) then was slowly pumped into the reactor at a slov rate such that the reaction pressure was about 1 psig. This pressure corresponds to an EO flow rate of approximately 300 g. of EO per hour. During the addition, the reaction temperature gradually increased to about 50*-60*C. After 4 hours, approximately 1200 g. of EO had been added for copolymerization with the charged THF reactant.

The rate of £0 addition then was slowly increased during about an hour so that a reaction pressure of about 5-8 psig was reached. Thereafter, the reaction mixture is maintained at this pressure for 3 hours while the reaction temperature was controlled at 60*C.

The rate of EO addition then was increased within a period of about 15 minutes until the reaction pressure reached about 20 psig. Meanwhile, the reaction temperature was controlled at 60"C. The remaining £0 reactant then was added for about 2-1/2 hours. Then the mixture was stored for an hour.

The reaction product was then purged with nitrogen for 15 minutes, cooled to 35*C, and discharged. Magnasol (50 g.) was added and the mixture was stirred for 2 hours at 65*C. The Magnasol was removed by filtration and the product was vacuum stripped at 60*C. with a slight nitrogen sparge. The product was a clear, colorless, viscous fluid.

EXAMPLES 2 - 10

The procedure of Example 1 was followed using different amounts of the THF monomer reactant, initiator and catalyst, and £0 rate of addition. The products obtained were liquid surfactant polymers of varying molecular weights having effective surfactant and other physical properties.

The process parameters of Examples 1-10 are shown in Tables 1 and 2 below.

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TABLE 1

PREPARATION OF LIQUID SURFACTANT THF-EO POLYMERS OF INVENTION

BF ₃ Aaounts (g) and Total Molar Ratl<os

Etherate Tiaeβ of EO EO of Components

Ex. No. THF (g) Starter (g) Catalyst (9) Addition (hrs.) Added (g) of Polymer

Stage A Stage B Stage C B ₁ D THF E0

C 3

CO 1 6616 Butanedlol (256) 10 1200(4) 1500(3 55(2.5) 3258 1 42 26

C r 2 1008 Butanediol (90) 2.5 300(3. 5) 300(2) 400(6) 1012 1 14 23

3 1632 Butanedlol (135) 2.5 250(4) 250(3) 140(1) 640 1 14 10

-H. nr» 4 648 Butanediol (90) 2.5 250(3) 250(2) 150(5) 651 1 9 14

C 5 5040 Butanedlol (225) 2.5 1500(5) 1500(3) 4502(8) 7502 1 28 68

Ξ m3C-_ 6 1314 Glycerol (55) 2.5 250(3) 200(3) 183(3) 633 1 42 24

7 1260 Glycerol (46) 2.5 350(4) 300(4) 604(6) 1254 1 35 57

8 958 Butanol (70) 2.5 200(3) 200(3) 1147(8) 1547 1 14 37

9 1260 Butanol (37) 2.5 300(4) 300(3) 720(8) 1320 1 35 60

10 982 Decanedlol (113) 2.5 200(3) 300(3) 951(7) 1451 1 21 51

The molecular veights, surfactant and other physical properties of the polymers of the invention are shovn in Table 2 belov.

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CO PROPERTIES OF LIQUID SURFACTANT THF-EO POLYMERS OF INVENTION

m Surface

Ex. Mol. Viscosity Foam Ht. Pour Point Cloud Point Lubricity Tension

No. Ht. (ops) (Ml) (•C.) ( ^• C.) (pel) (dynes)

1 3750 2100 5 -4 11-14 3180 0.1 0.01 0.00

2 1940 950 10 -22 24-27 1980 38.9 42.1 45.1

3 1360 380 0 -40 20-24 41.0 43.5 45.β

4 1230 420 20 -34 40-43 38.5 40.5 43.0

5 4800 9100 30 -2 35-38 39.9 43.9 48.9

6 3725 4000 15 -2 11-12 3220 42.2 44.1 49.2

7 4870 14000 30 0 42-44 2200 49.7 52.1 55.b

8 2525 1275 10 -20 30-35 39.8 41.5 50.0

9 5000 8920 40 -2 25-28 40.1 41.5 49.8

10 3760 540 20 -30 23-25 37.1 39.4 46.0

Mol. Wt. - Determined by OH number

Viscosity - Brookfield viscosity at 26*C.

Foam Ht. - Rose-Miles method at room temperature - 0. It solution

Cloud Point - 1% solutioni in water

Lubricity - Falex test. apparent gage load at failure, neat

The results in Table 2 show that the liquid surfactant polymers of the invention have excellent surfactant properties, as evidenced by the substantial surface tension reduction. In addition, these surfactants exhibit low foaming, low pour point and excellent lubricity properties.

Although the invention has been described with reference to certain embodiments thereof, it will be understood that changes and modifications may be made which are within the skill of the art.

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