CA1201844A - Phenolic resin compounds - Google Patents

Abstract

PHENOLIC RESIN COMPOUNDS A phenol-aldehyde resole resin is disclosed which is produced in the presence of a plasticizing amount of a phenolic ester of a fatty acid. These compositions are characterized by improved flexibility and moisture resistance. The resins are especially useful for impregnating cellulosic materials. Particular utility has been found for these compositions as filter elements wherein the impregnated cured paper can be corrugated after curing without cracking to provide an economical and superior filter paper.

Description

~L201B44 PHENC)LIC RESIN C~:)MPOUNDS

BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to internally plasticized phenolic resin compositions. More particularly, this invention relates to a composition, 5 Q process for the preparation of, and the use of a phenolic resole resin internally plasticized with a phenolic ester of ~ fatty acid.
Description of the Prior Art Phenol-formsldehyde condensates of the resole type are used extensively to treate cellulose compounds and particul~rly to impregnate 10 paper substrates. Upon curin~ to a ~ substantially insoluble and infusiMe stage, the resinoais material imparts chemical resistance and structur~l strengths to the substrates for use in a~ variety of applications. A
specific application for a phenolic resole in this manner is in the m~nufacture of filter media for both air and oil filtering systems and 15 p~ticularly for both stationary and mobile internal combustion engines.
The fabrication of filter structures of the foregoing type involve the following manufactur;ng operations. In the first or treating step, a continuous roll of paper is eonYentionally impregnated with a phenolic resole in the form of ~n alcohol solution of a condensate of phenol 20; wi~h formaldehyde. The saturated paper is heated to remove solvent ~nd the trested paper is then corrugated for the purpose of increRsing surf~ce area. The corrugated sheet is subsequently conveyed through An oven in order to advance the cure oî the resinous impregnate to fusible intermediate or B stage, and then rolled again. B staging may 25 be immedi~te to or time removed from the s~turation step.

~;2iO 1134 ~

The roll~ of the partially cured corrugated impregnated paper ar~
provided in this manner ~o the filter manufacturer for completion of the rnEmufacturing sequence~ The latter initially involve~ appropriately pleating the p~per and then heat-curing it to the final thermoset stage 5 in order to achieve a desired degree of chemis!at, oil and rnoisture resistance for the filter medium.
The standard phenolic resins used to treat filter paper have a disadvantage in that the number of folding or corrugating operations involved in the manufacture causes the ~ilter material to be brittle and 10 crack. Numerous plasticizers which have been developed to eliminate this difficulty haYe not been entirely satisfactory~ &enerally speaking, plastieizers of low molecular weight have a disadvantage in that they are eventually dissipated with the lapse of time &nd thus the compositions are rendered brittle. This is especially true when there is some hiatus 15 in the manufactllring procedure. Plasticizers of high molecular weight preclude such phenomenon, but compatibility problems with the base resin can occur.
Additionally, thermosetting resins such as phenol-formaldehyde resins have been used extensively as adhesives, laminates, molding 20 materials, paints and the like and improvements to improve flexibility without decreasing tensile strength are desirable along with improved moisture resistance for these purposes. Therefore, ~ need exists for an economical and efficient plasticized phenol-formaldehyde resin composition to overcome the shortcomings of ~he conventional plasticized 25 phenol-formaldehyde.
SUMMARY OF THE INVENTION
The present invention provides internally plasticized phenol-aldehyde resin compositions, a process for preparing these compositions ~nd the use OI these compositions as impregnating and/or laminating 30 agents for various substrates but particularly for cellulosic materi~ls.
- In accordan~e with this invention there is provided a thermosetting phenolic resin cornposition comprising a phenol-aldehyde resole resin in the presénce of a plasticizing amount of a phenoi ester of a higher f~tty acid containing from 8 to 22 carbon atoms.
In addition, the invenUon contemplates a process for preparing phenol-adehyde resole resin composition which comprises the steps of:
~) form~ng an aqueous alkaline mixture of phenol-aldehyde and a plasticizing amount of a phenolic ester of a fatty acid containing 8 to 22 carbon aton-s; and 5b) reacting this mixture under alkaline conditions to provide an internally plasticized phenol-aldehyde resole resin.
The phenolic ~;ter fatty aci~modified phenol-aldehyde resin ~ompositions of this invention are characterized by being internally plastici~ed, having more linear chains, limited branching and a lowered 10 cross-linking index which results in increased resin flexibility in increased flex fstigue resistance and in moisture resistance. These resins can readily be produced with very low (e.g., less than about 1%) free formaldehyde.
The present inven$ion also' contemplates a cellulosic substrate 15 i'mpregnated with a dried and cured resin composition of the present i~vention and, particularly, contemplates paper filter elements.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The ester employed in accordance with this invention is an es~er of a phenol and a fatty acid. The phenol moiety can be phenol per 20 se, m-cresol, ~cresol, ~cresoi or aIkyl derivative of phenol, such a t-butylphenol octylphenol, snd the likeO Among these) phenol itself is preferred.
The f~tty acids contemplated for use in this invention are saturated or unsaturated fatty acids containing 8 to 22 csrbon atoms. Such fatty 25 acids may be obtained from oils including drying oils and semi-drying oils. Specific represent~tive oils include soyabean oil, linseed oil, coconut oil, tall oil, safflower oil' and the like. Soyabean oil and tall oil are preferred due to economical advan$ages. Of course, fatty acids obtained from other sources and purified fatty acids can slso be used~ The fatty 30 acids include,_ter ~, capric, lauric, linoleic, linolenic, myristic, oleic ond palmitic acids.
The phenolic ester plasticizer can be produced by the use of acid catalysts and by carrying out the esterîication reaction under moderately elevated ' reaction conditions. Accordingly, the reaction can be 35 ~ccomplished efficiently by refluxing A mixture of the higher fatty acid ~LZ018~

and phenol in the presence of a small amount of a minerQI acid as caSalyst. The process involved is an equilibrium reaction and the attainment of equilibrium is greatly enhanced by a trace of hydrogen ion. ~hese reacUons can take place at reflux temperatures from about 5 110 to about 200C. There is nothing particularly critical in carrying out the reaction in this temperature renge and, indeed, if longer reaction times can be tolerated, lower temperatures can be used including the use of vacuum for refluxing purposes. At the end of ~he reaction, the lly~l~ogen ion in the mixture is desireably neutralized (e.g., as by ~dding 10 a base such as sodium hydroxide). Other methods of producing the ester are known in the art.
The esters are not soluble in water but they are soluble in a basic aqueous solutiQn of phenol and aldehyde such as that conventionally used in the manufacture of a phenol formaldehyde resole resin.
Commercial fatty acids obtained from refined tall oil may contain small amounts of rosin acids as impurities. If rosin acids are present, neutralization after esterification with sodium hydro~ide can result in the formation of undesireable lumps in the ester solution. This can be avoided by the use of a basic amine (e.g., diethyl or triethylamine~ for 20 the final neutralization.
According to the present invention, the phenol and aldehyde are reacted t~ form a resole in the presence of a plasticizing amount of the phenolic ester. Such reac~on generally follows the reaction conditions normally observed for preparing converltional resole 25 condensates, namely, the use of a basic catalyst and carrying out the condensation under moderately elevated reaction condition. This invention broadly contemplates the use of resole versus resins which are well known in the art.
In a resole, the phenol, which may be phenol itself or a substituted 30 phenol such as described above, is often reacted on the basis of one mole ~tnth rom about 1 to about 1.8 moles of the aldehyde. ~lore preferably, from about I to about 1.4 moles of aidehyde are employed per mole of the phenol. Aldehydes which can be used inelude7 formaldehyde, acetaldehyde, propionaldehyde, ben~aldehyde, furfural, or 35 the like. Formaldehyde is preferred îor the practice of this invention ~2~18~4 ~nd can be supplied to the re~ction mixture, for example, as formalin or paraformaldehyde.
As in the preparation oi conventional resoles, 1I basic cat~lyst is used. Representa~ive catalysts are the hydroxides of alkali metals with S sodium hydrox;de most often chosen for use. Conventionally, the pH
of the medium is maintained above 7 a~d often from about 7 to about 9.
The amount of e~;ter added to the reaction mixture will vary depending upon the particular properties desired for the end product.
10 The amoun$s suitable for any given application readily can be determined by one of ordinary skill in the art. Generally, however, the ester will be ~dded in amounts ranging from about S to about 20% by weight based on the total weight of the phenol-formaldehyde resin and ester solids. However, in some applications, such as coatings, the ester may 15 be present in amounts of up to about 50% or more.
The condensation reaction is generally carried out until the resole contains less than about 1% frèe ~ormaldehyde. Such resin is capable of curin~ to a thermoset condition in from about lûO to about 150 sec.
in accordance with the Stroke cure test. This is a standard test 20 procedure prevalently used in preparing a phenolic resin in order to determine an end point of a cook. In accordance with the test, a one-half gram sample of the reaction mixture is spread upon the surface of a cure plate maintained at 150C ~o coYer an area of approximately

2 square cm. The time in seconds is then noted when the film sets 25 up to a hard infusible stage.
Upon obtaining an end point as noted, the reaction mixture cormentionally is cooled to a temperature in the range of from about 40~ - 60 C and vacuum dehydrated. The~ dehydration is carried out until the free water or moisture content is not in excess of about 5 30 weight percent. The Karl Fischer moisture determination method (ASTM
Method E203) is the procedure conventionally used ior this purpose.
After the requisite degree OI dehydration is realized the deHydrated product is cut back Mth ~ polar solvent to provide a solution usually containing from 50 ~ 65 percent solids. The lower alcohols represent 35 the preferred solvents although ketones and the like can be used.

8~4 The improved properties, and especially the improved foldability resistnnce, flexibility and moisture resistance characl:eristics exhibited by the phenolic fatty acid ester-plasticized pheno}formaldehyde resole resin compositions of this invention make them emimntly suitable for 5 a wide variety of en~uses such ~s adhesives, impregnating agents, insulating materials, laminating resins, molding and reinforcing materiRls, p~ints, coating resins and the like. The resins of this invention ars useful for imparting the improved characteristics to any porous sheet material (organicJ inorganic or mixtures thereof) having pores extending lO from surface to surface. Two or more layers of the same or varying porosity can be employed in close juxtaposition, or even bonded together, but also spaced apart by suitable spacing sheets.
The invention is applicable to papers and like sheet materials formed of any type of fiber including not only cellulose fibers, but also 15 synthetic thermoplastic and nonthermoplastic resin fibers, glass fibers and fibers of other cellulose derivatives. Also useful, in addition to papers, are textile fabrics and woven and nonwoven fibrous layers such as felts, mats and bats made of fibrous materials of any of the types listed above. Such materials can also contain pigments and other 20 particulate matter.
Typicslly, an impregnated sheet member will contain from about 5 to about 20 weight percent (based on total impregnated sheet member weight? of solids derived from the phenolic resin of this invention.
Preferably, this impregnated sheet member has such solids substantially 25 uniformly distributed throughout such member. As noted earlier, the resin composition of this invention is particularly suitable for filters including oil filters for automobiles and the like.
The internally pl cticized phenolic resins of this invention can also be used alone or as a mixt~e with conventional phenolic resins for 30 preparing varnishes, coRtings or ~he like. Luminfltes can ~lso be produced by molding materials impregnated with the resin OI this rnaterial. Such laminates, coatings ~nd the like ha-/e excellent flexibility char~cteristics and moisture resistance.
Further detsils regarding the preparation of the phenolic resins 35 of this invention are given in the following working example which is included for illustrative purposes and is not intended to limit the scope of the invention. All parts and percentages noted therein are by weight ~less otherwise indicated.
EXAMPLE I
5 Part A
A suitable mixing vessel equipped with an agitator and a heating means was charged with 70.23 parts of soyabean fatty acid (Proctor and Gamble product S-210). To this, 24.82 parts of phenol ~99.8%) w~;
added. This mixture was agitated and heated to 50 C. At 50 C, 2.61 10 parts of sulfuric aeid (9~.4%) was charged to the fatty aeid -- phenol mixture over 8 2 minute period. The contents of the vessel were agitated and heated over a period of 4 hours to 204 C. The contents were reacted for 15 minutes at 204 C and allowed to cool to 135 C, at which point 2.34 parts of sodium hydroxide (50%) was added to 15 neutraiize the material. The materi~ was discharged into a clean dry container. The properties OI the resultant ester were as shown in Table L

Table I
pH: 6.5 20 Specific Gravity: 0.986 % Free Phenol: 11.5 Solid Content: no cure unless crosslinked with resin Viscosity: 800 cps Part B
To a suitable mixing vessel equipped with an agitator, thermometer, a heating means and a condenser, 1835.6 parts of phenol ~99.8%) was added. To t.his, 1196.0 parts of formaldel)yde ~50%) was added (to provide 1.02:1 ratio) and 383.8 parts of the ester described in Part A was added and ~gitated.
To this mixture 39.2 parts of sodium hydroxide ~25%) was added.

This ~git~ted rnixture was heated to 60 C and allowled to exotherm to ~5 C. The mixture was reacted at 95 C while monitor;ng the pH.
During this reaction 17.12 p~rts additional sodium-hydroxide was added to maintain a pH of 7.0 - ~.5. The mixture was reacted ~t 95 C to 5 ~ percent Free Formaldehyde of 1.0% or less (as determined by G.P.A.M.
203.3) and a 150 C hot plate Stroke cure (~s deterrnined by G.P.A.M.
207.1) of 1~0 secondc;. The resin was then cooled to 60 C and the reaction vessel set up for vacuum distillation.
The resin was then distilled at 60 - 65 C under 23-24 inches of 10 vacuum until 607 parts water had been removed into a distillation flask.
The mixture was cooled to 40 C and 633.85 parts methyl alcohol as well as 58.75 parts methyl ethyl ketone were added. The physical properties were as shown in Table 2.

Table 2 l 5 ViscositY~ ~30 cps Specific Gravity: 1.100 pH: 7.7 Refractive Index 1.5250 150 C Stroke cure: 121 % Free Phenol: 11.34 % ~ree Formaldehyde: 1.00 Solids Content: 65.00 % Water: 4,30 Apparent average Molecular Weight: a4s4 EXAMPLE II
The ester modified phenolic resin produced in Example I was eYaluated as a filter paper impregnant noting the relevant physical properties " :

parti~ularly with regard to fold fatigue characteristics imparted to the filter paper both before and after curing the treated pl~per. The latter properties were determined in accordance with standardixed test methods.
For comp~rision purposes several commercial phenolic resins 5 conventionally used were included and referred to hereinbelow as exemplary of the prior art.
In conducting these tests 6" x 8" size sheets of standard filter paper were impregnated with the respective resin solutions (diluted with methanol) to provide about 28% ~ 0.3% resîn solids pick-up. The 10 procedure for treating the impregnated paper in order to advance the resin component to a B stage involved air drying and then heating in a forced air oven at 150 C for 2 minutes. The paper was conditioned at 60% Relative Humidity for 10 minutes. Strips 1/2" x 4" were cut and then placed in a Tinius-Olsen fold tester. The number of folds 15 were counted at 0.25 kg tension until the paper breaks. Three commercial phenol formaldehyde resoles resins, GP 5157 (Resin A); GP
5165 (Resin B); and GP 5135 (Resin (~) (all available from Georgia-Pacific) ... .
were used for comparison. All three GP resins are NaO~catalyzed resole resins. GP 5157 has a formaldehyde phenol mole ra~io of 1.1:1, a 20 pH of 7.2-7.8, a solids content of 60-62%, a specific gravity of 1.124-10138 ~nd a 135 C Stroke cure of 2-4 minutes. GP 5165 has a formaldehyde:phenol mole ratio of 1:1, a pH of 7.6-8.2, a solids content of 62-66%, a specific gravity of 1.110-1.160; a H20 content of 4-5% and 150 C Stroke cure of 90-120 sec. GP 5135 has a formaldehydP:phenol 2~ mole ratio of 1.16:1, a pH of 7.8-8.2, a solids content of 62-66%, a specific gravity of 1.116-1.124, a ~2 content of 3-5%, ~nd a IS0 C
stroke cure of 60-80 sec.
The results of all tests are set forth in Table 3.
Table 3 30 TestInvention Resin A Resin B Resin C
1. 63 2 10 5 a. 48 1 9 4

3. 71 2 8 5

4. 39 a ~ 5

5, 47 2 7 5

6. 58 2 8 4 l344

7. ~l 3 6 5

8. ~2 2 1~ 4

9. 63 2 9 4 lO. 59 l 8 5 The fold test results clearly indicate that the este~modified phenolic resin imparted superior flexibility and flex fatigue resistence, on B staged paper than the other conventional resins so treated. This data also indicates that the ester provided intern~l plasticization for the phenol aldehyde resin. Furthermore, liquid chromatographic analysis OI $he conventional phenolic resin compared with the ester-modified phenolic resin indicates that incorporation of the ester ties up some of the reactive sites on the phenol component of the phenol formaldehyde resin and in turn methylation and condensation are somewhat retarded.
Chromatograms generally show lower apparent molecular weight fractions with the incorporation of the ester. The tying up of reactive sites on the phenol allows a more linear chein polymer with limited branching and lower crosclinking indexes.
Since modifications will be apparent to those skilled in the art, it is intended that this invention be limited only by the scope of the 20 appended claims.

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Claims (16)

1. A thermosetting phenolic resin compositions comprising a phenol-aldehyde resole resin produced in the presence of a plasticizing amount of a phenolic ester of a higher fatty acid containing from 8 to 22 carbon atoms.

2. The composition according to claim 1, wherein said fatty acid is selected from the group consisting of capric, lauric, linoleic, linolenic, myristic, oleic and palmitic acids.

3. The composition according to claim 1, wherein said phenol component of the ester is selected from the group consisting of phenol, m-cresol, p-cresol, o-cresol, t-butylphenol, or octylphenol.

4. The composition according to claim 2 wherein said fatty acid is derived from soybean oil.

5. The composition according to claim 1 wherein said fatty acid is derived from tall oil.

6. The composition of claim 1 wherein said ester is present in an amount of from about 5 to about 20% by weight based on the total phenol-aldehyde resin and ester solids.

7. The composition according to claim 1 wherein said resole resin is phenol-formaldehyde resole resin.

8. A process for preparing a phenol-aldehyde resole resin composition which comprises the steps of:
a) forming an aqueous alkaline mixture of phenol, aldehyde and aplasticizing amount of phenolic ester of higher fatty acid containing 8 to 22 carbon atoms; and b) reacting the mixture under alkaline conditions to provide an internally plasticized phenol aldehyde resin.

9. The process according to claim 8 wherein the mole ratio of aldehyde to phenol in the resole ranges from about 1:1 to about 1.8:1.

10. A flexible substrate impregnated with a thermosetting phenolic resin composition comprising a phenol-aldehyde resole resin produced in the presence of a plasticizing amount of a phenolic ester of a higher fatty acid containing from 8 to 22 carbon atoms.

11. The flexible substrate according to claim 10, wherein the phenol-aldehyde resin is phenol-formaldehyde, the phenolic component of the ester is phenol and the fatty acid is derived from tall oil.

12. The flexible substrate according to claim 10, wherein the substrate is paper.

13. The flexible substrate according to claim 10, wherein the flexible substrate is cork.

14. A filter element comprising a cellulosic base member impregnated with a thermosetting phenol-aldehyde resole resin produced in the presence of a phenolic ester of a higher fatty acid containing from 8 to 22 carbon atoms.

15. A filter element comprising a cellulosic base member impregnated with a cured phenol-aldehyde resole resin manufactured in the presence of a phenolic ester of a higher fatty acid containing from 8 to 22 carbon atoms.

16. An automobile oil element according to claim 15.