Preparation and Properties of Alkvlnhenol-Acetylene Resins J
L
J
A. 0. ZOSS, W. E. HANFORD', AND C. E. SCHILDKNECHT General Aniline und F i l m Corporation, Easton, Pa. Resins prepared by the catalytic reaction of p-allcylphenols with acetylene in the presence of an inert diluent at elevated temperature and pressure, and obtained in the molecular weight range of 800 to 1100, are brittle solids resembling, in some respects, the oil-soluble alkylphenolaldehyde condensation products, The p tert -butylphenolacetylene resin, known as ICoresin, develdped first in Germany and now made in this country is one of the most effective tacltifiers for Buna S and GR-S known. In addition to duplicating the foreign-made material, several reaction variables were studied. Also, p-tert-amylphenol and diisobutylphenol were made to react with acetylene to form products similar to Koresin, but of somewhat lower tack values and melting points. The physical prop-
erties studied included solubility, compatibility, cloud point, melting point, molecular weight, stability, inhared absorption spectra, and x-ray pattern. Observations on the methods of application to synthetic rubbers and other possible uses are given. A discussion of the reaction mechanism and polymer structure is included and the following formula is proposed:
R
In a 2.7-liter stainless steel autoclave having a working pressure of 1700 pounds per square inch were placed 500 grams, 3.3 moles, of p-tert-butylphenol, melting point 97" C. To this were added 43.8 grams of zinc naphthenate having a zinc content of 12%. The autoclave was closed, the a p aratus was pressure-tested at room temperature with 200 p o u n i per square inch nitrogen ressure, and then the entire system was flushed repeatedly witE nitrogen to reduce the oxygen content t o below 0.50J0. The contents were heated t o 210" C. during 1 hour and the nitrogen pressure was adjusted t o 140 pounds per square inch. While maintaining this temperature, acetylene was added t o make the total pressure 200 pounds per square inch. The drop in pressure, due t o reaction, was made up by the addition of fresh acetylene from the cylinder. This gas mixture is analyzed periodically to see that the acetylene content does not exceed 30%. [With diluents other than nitrogen the proportion of acetylene could be varied t o maintain a safe concentration ( 2 ).] When the Ubbelohde (13) drop point of a sample exceeded 135 C. the acetylene addition was stopped, the system was flushed with nitrogen and the contents were discharged. The molten material was degassed and packaged. The yield varied generally from 630 t o 664 grams of product, which was e uivalent t o a n acetylene consumption of 3.3 to 4.6 moles. &us, the mole ratio of p-tert-butylphenol t o acetylene in the product was 1 to 1 t o 1 to 1.4.
-
ESINS prepared by the catalytic reaction of p-alkylphenols with acetylene in the presence of an inert diluent at elevated temperature and pressure (28, 24), and obtained in the molecular weight range of 800 to 1100, are brittle solids resembling, in some respects, the oil-soluble alkylphenol-aldehyde condensation products. Both types have one important use in common, that of promoting the tackiness of synthetic rubber (1,251. The p-tert-butylphenol-acetylene resin, known as Koresin, developed first in Germany and now made in this country, is one of the most effective tackifiers for Buna S and GR-S known (2, 8, 18, 14, 21, 26). This material is superior to the alkylphenolformaldehyde product when used as a tackifier for GR-S, for it has practically no effect on the cure. Since the main objective of this work was the duplication of the German synthetic tackifying agent, Koresin, most of the reaction conditions were studied using p-tert-butylphenol as reactant. The reactions of some higher alkylphenols with acetylene were examined also. Physical properties and applications of Koresin were studied and a discussion of the reaction mechanism is included.
REACTION VARIABLES
Using the above procedure as a basis the effects of certain EXPERIMENTAL PROCEDURE variables on the rete of reaction and quality of product were A typical reaction procedure for the synthesis of Koresin is studied. These factors investigated were: concentration of zinc given below and the proposed resin structure is shown. naphthenate, catalysts other than zinc naphthenate, effect of pressure, purity of butylphenol, and use of higher alkylphenols. The factors, temperature and acetyOH r OH lene concentration. were held constant. As a measure of quality, the tack values were determined in catalyst, diluent HCsCH the authors' physics laboratory by Busse, Lambert, 210" C., 200 pounds per square inch and Verdcry (1). lq-iH-jn amount CATALYST of zinc CONCENTRATION. naphthenate onThe acetylene-p-terteffect of the
a
YH8
+
1
-f
butylphenol reaction time is shown in Table I. Varying the concentration from 8 t o 4% had little effect on the rate. However, reducing the concentration t o 2% caused a considerable slowing up of the reaction. Also, the tack value of the product formed from this latter reaction was lowered.
R = tert-alkyl group: C I ,Cg,C6, etc. n =4to6
Precautions were taken for handling acetylene safely under pressure (9). 1 Present address, M. W. Kellogg Company, New York, N. Y.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 41, No. 1
butylphenol-acetylene resin as higher tJhari those of the other
TABLEI. EFFECTOF ZISC NAPHTHESATECOKCENTRATIOS two products. Zinc SaphExfperithenate*, inent 70 NLmber 8 1 2 4 2 3
Reaction Time, Hr. 2.4 2.3 6.0
p-teli-Butylphenol t o 4 c e t y l e n ~ , L-bbelohde Tackc, Oz. Drop after 24 Mole Ratio Temp., C. Hr. in Product 1:1.4 165 0 16 15 1:I.l 155 0 1:1.4 158.0 13
Per rent zinc naphthenatc as calculated from weight of p-tert-butylphenol plus zinc naphthenate charged t o autoclave. Corresponding metallic zinc Dercentaees a s calculated are 1.0, 0.5, and 0.2, respectively, f o r 8, 4, a n d 2% &no naphxhenate. b Cbbelohde method for determination of drop point ( 1 3 ) . Force required to separate surfaces undei test; accuracy = * l or 2. Tack value of blank = 1 ( I ) .
(:.ITALYSTS OTHER THAN ZINC NAPHTHENATE. A number of other zinc and cadmium carboxylic acid salts acted as catalysts to produce Koresinlike products. These included zinc acetate, zinc laurate, zinc linoleate, zinc oleate, zinc palitate, zinc resinate, zinc stearate, cadmium acetate, and cadmium naphthenate. Cyclohesglaniine also catalyzed the alkylphenol-acetylene reaction to give a resinous material. EFFECTOF TOTAL PRESSURE. The effect uf pressure on the reaction b e h e e n p-tert-butylphenol and acetylene vas examined. All other variables were maintained essentially constant. The data in Table I1 show that the reaction time was increased by reducing the total pressure.
TABLE11. EFFECT OF PRESSURE Total Experi- Reaction Pressure. ment S u m b e r Lb./Sq. In. 1 200 2 110
3
80
n-tPrt-Riitvl.. . - - _ I .
Reaction Time, Hr. 2.4 9 .o 9.5
phenol t o Acetylene, hlole Ratio in Product
Ubbelohde Tack, Oa. Drop after 24 Temp., C. Hr.
1:1.4
155.0
1:1.4
146.0 130.0
1:1.3
16
14
13
PHYSICAL PROPERTIES OF THR HESIIVS
APPEARAKCE.Koresin is a tan-to-brown, brittle, hard solid superficially resembling rosin. Granules of Koresin do not adhere t o form a solid mass on storage a t room temperature or even after heating for 100 hours at 50 O C. SOLUBILITY AND COJIPATIBILITY.Koresin, to a certain est,ent, resembles in solubility and compatibility the oil-soluble alkylphenol-aldehyde resins. Horn-ever, in contrast t o many coinmercial alkylphenol-aldehyde resins, Koresin possesses good compatibility combined with relatively high softening point, properties which are retained on storage and even on heating a t elevated temperatures. Solubilities of t'he resins in various materials are shown in Table V. I n general the resins made by catalyzing the p-tertbutylphenol-acetylene reactions with zinc and cadmium salts other than zinc naphthenate showed similar solubilities 60 those made by use of t,he latter catalyst. In the compatibility tests shown in Table VI equal m-eights of a 5% solution of Xioresin in toluene and of a 5% solution of the other polymeric material dissolved in the solvent indicated were mixed thoroughly. The solutions stood at room temperature 24 hours and were examined. Films were then cast on glass by heating at 50 * C. for 15 hours. Clarity of the solutions and of the cast film was the criteria of compatibility. Koresin is also compatible with natural rubber and GR-S mixtures, and under certain conditions may be compatible with polyethylene, asphalt, polyamide resins, neoprene, and Hycar
OR. CLOUDPOINT-S AND MELTINGPOINTS. Cloud point and melting point data are given in Table VII. The procedure for determining cloud points was described by Powers (19). In addition to the ball and ring method, melting points were obtained by the Ubbelohde drop point method (IS) and by the capillary tube method. As the data under the reaction variables section showed, the melting points of the good quality resins, from the viewpoint of tack, were in the range of 102" t o 177" C. (Ubbelohde). By the capillary tube method melting points about 20' C. lower were observed (6). The melting point depended upon type of phenol used and upon molar ratio of reactants combined in the product. In general, for an approximate 1 to I molar ratio in the p-tert-butylphenol-rtcetylene (Koresin) system, the Ubbelohde drop temperature was in the range of 120" to 160' C. A lower acetylene content resulted in a lower melting point product and a higher acetylene content resulted in a higher melting point product. Thus, a p - t e r t butylphenol to acetylene ratio ranging from I to 0.9 to 1 to 1.5
Several butylphenols of varying PURITYOF BUTYLPHE~OL. purities were examined. The experiments are summarized in Table 111. For comparison a typical experiment with pure inp-tert-butylphenol was TABLB1x1. EFFECT O F PURITY O F p-tWt-BUTYLPHENO1; cluded. It can be seen from Butylphenol Table I11 that the tack values Reaction to Acetylene, Ubhelohdr Tack, 0 2 , Experiment Wt., Time, Mole Ratio Drop after 24 of the products made from Number Material, Analysia Grams Hr. in Product Temp., OC. Hr. the crude butylphenols were 1 85% butylphenol 510 4.1 1:1.2 < 100 8 101-2% butylphenyl etLer lom-er than from the pure p 3 4 % phenol b ie,t-butylphenol. Also, the a 600 2.2 117 9 3 92% g-tert-butylphenoi 450 3.0 1:l.l 129.5 13 Cbbelohde drop temperatures 87' 6-tert-butylphenol 4 80% p-tert-butylphenol 406 2.1 1:l.l 116.0 13 were lower. 2Od o-tert-butylphenol 5 74Y0 plerl-butylphenol 396 3.0 1:l.Z 11.2,o 9 HIGHER ALKYLPIIENOLS. 18% o-lert-butylphenol Resinous products were ob8% dialkylphenol 6 Pure (melting point 97' C.) 600 2.4 1:1.4 155.0 16 tained by reacting p-tertamylphenol, p-(l,l,3,3-tetrsAnalysis not available b u t expected to contain loss butylphenyl ether and phenol than material in Experiment 'I . methylbutyl)phenol, as we11 b Sinco analysis is unknown, this caloulation ia uncertain. If this were 100% p-tert-butylphenol, ratio would be 1:l.l. as p-tert-butylphenol with acetylene under comparable conditions using zinc naphthenate M A D E FROM VARIOUS p-kTt-ALKYLPHENOLS TABLE IV. COMPARISON OF RESYNS 8s catalyst. The products are p-tart-Alkylcompared in Table IV. These phenol t o Reaction Aoetylene, Ubbelohde Tack, OE. were all tan to brown brittle Experiment Phenol Time, Mole Ratio Drop after 24 Kind Molee Hr. in Product Temp., C . Hr. Number solids. The one made from 3.3 2 5 1:l.l 146.5 16 1 p-ferl-butyl the octylphenol had a some2.7 1.5 1:o.g 117.5 15 2 p-tsrt-amyl what lower tack value. The 1:l.l 128.5 13 3 ~(1,1,3,3-retramethylbutyl) 2.4 3 0 drop temperature of the p-ted(i
INDUSTRIAL AND ENGINEERING CHEMISTRY
January 1949
7s
APPLICATIONS OF KORESIN
01 BOO
1400
1600
1200
1000
800
FREOUFNCY CM-'
Figure 1.
Infrared Spectra of Koresins
Some of the various resins prepared were examined as tackifiers for synthetic rubber in t h e laboratories of the Firestone Tire & Rubber Company acting for the Rubber Reserve Corporation. A study of the tackifying properties of these resins has been published (1). Koresin waa shown t o be a n excellent tackifier for GR-S. With a few possible exceptions the tackifying action of Koresin seems t o be specific for butadienestyrene synthetic rubber formulations such as I 600 GR-S and Buna S. In order t o obtain good building tack from 5 t o 10 parts of Koresin are normally required t o 100 parts of GR-S (8). However, less than 5% has been found t o give improved tack of practical value, particularly with GR-S natural rubber mixtures. Koresin does- not retard cure and in some compositions an acceleration of cure has been observed. Tensile strength of the cured stock is ordinarily not
TABLEv.
SOLUBILITY
X-Ray Diffraction Patterns of Koresins A. B.
German American
Acetone Benzene Cyclohexane Petroleum ether Ethyl acetate Ethyl ether Methanol Ethanol n-Butanol Water Sodium hydroxide 10% Sodium hydroxide' 40% Sulfuric acid, 10%' Sulfuric acid, 94%
provided materials of melting points ranging from 110" t o 170 C. Products containing equimolar amounts of p-tert-amylphenol and acetylene or diisobutylphenol and acetylene had lower drop temperatures than the comparable p-tert-butylphenolacetylene resins (see Table IV) MOLECULARWEIGHTS. The alkylphenol-acetylene resins have molecular weights which are in the range of 800 t o 1100, as can be seen in Table VIII. The corresponding degrees of pol merization are about 4 t o 6 . &ABILITY. The p-tert-butylphenol-acetylene resins as obtained were stable to heat and to ultraviolet irradiation. Table IX shows comparative data derived from these tests. The tack value was not impaired by the tests described. IMPURITIES IN KORESIN. The resins as prepared contain varying amounts of free alkylphenol. Satisfactory products from the viewpoint of good tackifying properties for GR-S have less than 8% free alkylphenol in them. I n general, the higher t h e drop temperature of the resin, the lower the free alkylphenol content. It has been disclosed t h a t alkyl substituted phenols, including p-tert-butylphenol, are softeners and tackifiers for synthetic rubber (c5). Zinc naphthenate has been disclosed as a softening agent for rubber (S, 16). No outstanding difference in tack value was observed between the purified products and the reaction product. Steam distillation of Koresin results in the removal of a yellow oil of strong odor.
Resin or Plastic Bakelite Resinoid BR-9432 Bakelite BR-4036 Nevillac (hard) Neville resin R-7 Arofene 775 Polyisobutylene B-100 Butyl rubber Mille Mille Polyvinyl isobutyl ether Polyvinyl n-butyl ether Polyvinyl butyral (low OH type) Polymethyl methacrylate Polystyrene Polyvinyl acetate Ethyl cellulose
EVIDENCE FOR DUPLICATION OF KORESIN
Cellulose nitrate (film type) Cellulose acetate (low acetyl film type) Polyvinyl chloride
.
Infrared and x-ray coniparisons have been made of German Koresin and Koresin prepared in the authors' laboratory, as described in the experimental section. The infrared absorption spectra and the diffraction patterns are shown in Figures 1 and 2, respectively. Only minor differences are present. These are attributed t o differences in purity rather than t o a difference in kind. The solubility characteristics and tackifying properties of these two materials with the same GR-S are very similar. Table X contains a comparison of several additional properties of German Koresin with two of the authors' laboratory samples, one of a lower molecular weight and one of a higher molecular weight. The differences again are probably due to raw materials used and slight variations in reaction conditions.
a
P-tert-ALRYLPEE;NOI,-ACETYLENE
RESINS
Solvent
Figure 2.
OF
Solubilitya of Resins Made by Catalysis with Metallic salts Cyolohexylamine
++ ++ ++ ++ ++ ++ +++-
++ ++ ++ ++ ++ ++ ++ ++ ++ -
-
-
-
+t*
+ T b
+.+ High solubility, + fair solubility. - insoluble. Deep red solution; ;robably because 6f reaction.
TABLE VI. COMPATIBILITY OF KORESIN~
a
Second Polymer Solvent Toluene Toluene Toluene
Compatibility in Solution Film
++ 2 ++
-
T- n. l n e.. m~ .
Toluene Toluene
Ethanol Acetone
+ ++ + ++ +-
Cyclohexanone
f
Toluene Toluene Toluene Toluene Toluene Toluene Ethano!-toluene, 1:1
+++ ++ + +++ + - b
-b
-rb - b
+ -
4-
5 % Koresin in toluene plus 5 % resin in second solvent (equal weights).
Koresin is compatible a t lower concentrations.
TABLE VII. MELTINQPOINTS AND CLOUDPOINTS OF K O R E S I N ~ Cloud Point, Sample Solvent, aniline point Koresin, German, melting point 127' C. Koresin, American, melting point 124.6O C. b
*
Nujol 104
