MOULDING COMPOSITIONS INCLUDING UNSATURATED ESTERS AND AN AMIDE OF AN UNSATURATED ALIPHATIC CARBOXYLIC ACID

i0 Æ074038 The present invention relates to moulding compositions including an unsaturated polyester or a mixture of two different unsaturated polyesters, and an amide of an unsaturated aliphatic carboxylic acid, and the moulded articles obtained from the said compositions.

Unsaturated polyester resins consisting of the products of the polycondensation of unsaturated polybasic acids with polyvalent alcohols, in solution in styrene or another unsaturated liquid monomer, are known in the art.

The said resins harden under the action of catalysts such as the organic peroxides, possibly used in conjunction with polymerization accelerants, such as, e.g. cobalt naphthenate or octoate.

The unsaturated polyester resins find their main use in combinatiõn with reinforcers of a fibrous nature, for preparingmanufactured articles commonly know as "reinforced plastics".

The reinforcers commonly used for the purpose are•:

asbestos, cotton, jute and especially'glass, in fibre or fabric form.

Various" methods for moulding reinforced unsaturated polyester resins are known, which gènerally consist of arranging fibrous reinforcer in a suitable mould into which the liquid resin containing the catalyst for hardening is poured, or else the said resin is sucked or injected into the mould. •The resin is then hardened at high temperature, possibly under pressure.

Examples of these methods are: direct compression moulding, moulding by suction and injection moulding.

Also known is direct moulding with preforming, which D 1074038 consists of subjecting to moulding a "preform", made of glass fibre impregnated with resin and formed by suction in a suitable chamber, and by thermal treatment of the said• deposited material in a current of air.

These processes are somewhat onerous and do not allow high productivity of the moulded objects. The said moulded objects have, moreover, variousundesirable characteristics, such as, for example, the smell of the unsaturated monomer used in the resin in combination with the product of polycondensation of the unsaturated polybasic acids with the polyhydroxy alcohols. Finally, there are various difficulties in handling substances such as unsaturated polyester resins.

The thermoplastic resins, unlike the thermosetting ones, are moulded with great ease and speed, in apparatus in which they are first uniformly heated to fluidity and then injected into a mould in which hardening takes place.

The application of such a method to the thermosetting resins involves having available moulding compositions, comprising the thermosetting resin, a hardening catalyst, and an inert filler, possessing the following characteristics:

- stability in storage for long periods of time at ambient temperatures; - ability to change into the fluid state within temperature limits in which the phenomena Of premature cross-linking and hardening do not occur appreciably; - ability to harden rapidly at temperatures higher than those necessary to ensure fluidity of the mass.

Preferably, these moulding compositions should be in the form of easily flowing granules having no tendency to release dust.

bm/ i0 Æ07403.8 :

NO moulding compositions,.including an ûnsaturated polyester resin, possessing all the characteristics listed above are known. ..

Moulding compositions have now been found, which are stable at ambient temperature,, fluid withiñ temperature limits in which premature cross-linking and hardening do not occur, and which harden rapidly at high temperatures.

'The said compositions/ in flowing granular form, free from the tendency to release dust, are converted into moulded articles, by known methods, including injection moulding, in the same way as thermoplastic materials.

The moulded articles thus obtained have an unusual combination of characteristics.

Thus, the inVention provides a moulding composition comprising:

(a) from il0 to 50 Wto% of unsaturated polyester A and/or unsaturated polyester B, wherein:

said unsaturated polyester A is the polycondensation product of 2,2'-bis(4-hydroxycyclohexyl) propane or a halogenated derivative thereof, and an ethylenically unsaturated bicarboxyli¢ acid, having the following characteristics:

- meltìng point (at the capillary) >70°C - acid value (mg KOH/g) <50 - Gardner viscosity (at 25*C in 60 wt.% solution in styrene) from Y to Z3 , said unsaturated polyester B is the polycondensation product of an alkylene glycol, an ethylenically unsaturated bicarboxylic acid and a saturated bicarboxylic acid, having the following characteristics:

- melting pQìnt (at the capillàry) 60°C " bm/ - acid vàlue (mg KOII/g) <50 - Gardner viscosity (at 25°C in 60 wt.% solution in styrene) from U to Z2 ; (b) from 0.5 to i0 wt.% of an amide of an ethy!enically unsaturated aliphatic carboxylic acid; (c) from 0.2 to 2 wt.% of an organic peroxide having a decomposition temperature above 70°C; (d) one or more inert fillers.

In addition to the polyesters, the peroxide, the amide and the inert fillers, the moulding composition may also contain small amounts of conventional additives,; such as polymerization inhibitors, lubricants, dyes and pigments.

The preferred composition contains from 20 to 35% by weight of unsaturated polyesters A and B, from 4 to 8% by weight of'said amide and from 0.5 to 1.8% by weight of said organic peroxide. Particularly satisfactory results are obtained with compositions including the polyester A alone or mixtur.e of the polyesters A and B containing up to about 30 wt.% of polyester B.

The unsaturated polyester A As previously stated, the unsaturated polyester A is the polycondensation product of 2,2'-bis(4-hydroxycyclohexyl)propane, or a halogenated derivative thereof, and an ethylenically unsaturated bicarboxylic acid.

By halogenated derivatives of 2,2'-bis(4-hydroxycyclohexyl) propane are meant the chloro or bromoderivatives, in the ring and/or in the propane radical.

The unsaturated bicarboxylic acid is preferably chosen from fumaric and maleic acids.

The unsaturated polyester A which is preferred for the bm/ .x i0 " :1.074038 purposesof the present invention has general characteristics in the following ranges of values:

-. melting, point : from 80 to 95°c - acid value : from 15 to - Gardner viscosity : from Z1 to Z3 In the preparation of the unsaturated polyester A the reagents are placed in contact and polycondensed at elevated temperature, while removing.the water which forms during reaction, until the preselected acid value of the unsaturated polyester is reached.

The molar ratio between 2,2'-bis(4-hydroxycyclohexyl) propane or its halogenated derivative, and the preselected unsaturated bicarboxylic acid, is preferably maintained during the reaction at a value of from 1.05:1 to i.i:i.

According to a preferred embodiment, operation is carried out ata temperature of the order of 190-210°C, removing the water at atmospheric pressure, until the acid value of the unsaturated polyester is from about 50 to about 40, and then at subatmospheric pressure (for example 10-50 mm Hg) until the desired acid value is reached.

The bes,t,results are obtained with molar ratios between 2,2'ibis(4-hydroxycyclohexyl)propane or its halogenated derivative and the unsaturated bicarboxylic acid of the order of i.i:i.

The unsaturated po l.ygsteÇ B As previously stated, the unsaturated polyester B is the polycondensation product of an alkylene glycol and a mixture of ethylenically unsaturated bicarboxylic acid and bicarboxylic acid free from ethylenical unsaturation The glycols preferred for the purpose, are ethylene and bm/ "5i0 propylene glycols.

The unsaturated bicarboxylic acid is preferably chosen from maleic and fumaric acids, and that free from ethylenical unsaturation from phthalic, isophthalic and terephthalic acids.

The unsaturated polyester B preferred for the purposes of the present invention has general characteristics in the following range of values:

- melting point from 60° to 80°C - acid value from 15 to - Gardner viscosity from W to Y Production of the unsaturated polyester B is completely similar to that of the unsaturated polyester A, the molar ratio between the alkylene glycol and the bicarboxylic acids being preferably from 1.05:1 to i.i:i and the molar ratio between the ethylenically unsaturated bicarboxylic acid and that free from ethylenical unsaturation being preferably from I:i to 3:1.

Particularly satisfactory results are obtained by polycondensing isophthalic acid, fumaric acid and ethylene glycol.in molar ratios of 1:3.0:4.4.

The amide of the unsaturated carboxylic acid The amide is preferably chosen from those which can be defined by the general formula:

/R2 H2C = C - C - N I \ Il1 R3 wherein RI, R2, R3 are hydrogen or a lower alkyl group, such bm/ o i0 as, for example, acrylamide, methacrylamide, N-methylacrylamide and N,N-dimethy1 acrylamide.

The organic peroxide The organic peroxide suitable for the compositions of this invention has a decomposition temperature higher than 70°C aid preferably hoEgher than 120°C.

The said peroxide may be chosen from a wide class of compounds, for example:

- dialkyl peroxides, such as di-tert-butyl peroxide; - diaralkyl peroxides, such as dicumyl peroxide; - cyclic peroxides, such as dibenzylidene diperoxide; - peroxy-esters, such as tert-butyl peroxybenzoate and di-tert-butyl perphthalate; - peroxides of the metal1 type, e.g. that known commercially as "Trigonox 17/40".

The latter is used in combination with known polymerization accelerants, such as the cobalt, manganese, cerium, nickel and iron salts of organic acids and partigularly cobalt naphthenate and octoate.

The inert fillers and the other constituents of the moulding compositions The inert fillers are preferably chosen from silica, calcium carbonate, asbestos and glass fibre. The latter is generally present in the compositions in amounts of from i0 to 55% by weigh preferably in the form of fibres of the order of 3-10 mm in length.

The compositon of the present invention generally contains from 20 to 500 ppm (with respect to the unsaturated polyesters) of one or more substances chosen from among those conventionally used in the art to inhibit polymerization bm/ 'e v • ,• i0 Æ074038 of the uñsaturated polyester resins.

These inhibitors may be chosen from a wide-set of compounds, such as: quaternary ammonium salts, salts of amines, copper salts, nitrophenols, dihydric phenols and their alkyl derivatives.

The moulding composition generally contains from 1 to 3% by weight of a lubricant, preferably chosen from waxes, stearic acid and zinc, calcium and magnesium stearates.

Further additives generally present in the composition are dyes and pigments.

Preparation of the moulding composition The moulding composition of the present invention may be prepared in the following way. All the components except the glass fibre are fed into a ball mill and ground to a grain size'of the solid of less than about I0 microns.

Then the glass fibre is added, the mass is homogenized in a powder mixer, operating in conditions such that he glass fibre will not be broken, and the homogenized mass is calendered, operating for times of the order of a few minutes and with roller temperatures not above about 100°C, until a sheet of thickness of the order of 1 mm is obtained. This latter is ground, e.g. in a hammer mill, and the resulting granules are sifted in order to separate the fraction having the desired grain size. A moulding composition in the form of granules from 100 to 5000 microns, is thus obtained.

Absence of particles with dimensions less than I00 microns is preferable, or, at least, such particles should not exceed 5% by weight of the composition.

According to another procedure, after homogenization with the glass fibre, the composition is extruded, and the bm/ 4'.

ìl .x¢.

.o -- 8-- r r i0 granulate is obtained by means of "in-head cutting" of the extrudate.

The composition is stable at ambient temperatures for a period of time greater than three months and generally up to six months, especially if kept in watertight bags, e 9 ....

of polythene or polythene paper. Storage temperatures below the ambient temperature cause no damage. Moreover the said composition has no tendency to release dust.

The composition becomes fluid and flowing at a temperature from 120 to 130°C and at these temperatures it has a "plastic life" or useful time for working greater than 125 seconds up to 15 minutes or more.

Hardening occurs at temperatures of from 145 to 180°C, in times of the order of from i00 to i0 seconds.

The data relating to the "plastic life" and to the hardening speed were determined by means of the Brabender rheometer from Brabender Instruments Inc.

More particularly the said.rheometer comprises a cell with a device with rotors which can rotate at different speeds. The whole system is thermostatted.

The moulding composition is fedinto the cell. Under the action of the temperature and the friction of the rotors, the composition undergoes both physical and chemical changes.

The resistance with which the composition opposes the action of the rotors, expressed as a turning moment in revolutions per minute, is measured and recorded as a function of tìme.

It is thus possible to determine the softening, melting and hardening cycles of the composition under examination, bm/ -9i.

• v i0 obtainingusefui data for injection moulding.

Preparation of moulded articles Preparation of the moulded articles can be effected by normal methods of compression, transfer and injection moulding, using moulding cycles which are speedy.and completely automatic.

In direct compression moulding the mould can be filled at pressure of from 12 to 250 Kg/cm2, especially depending on the geometry of the article, with optimal moulding temperatures of from 145 to 165°C.

In transfer moulding the best results are obtained with directly incorporated chamber moulds, with the feed heads as short as possible and with a single injection per cavity.

Moulding temperatures are of the order of 145-155°C.

The bëst results are achieved by irìjection moulding in which the moulding composition is made fluid by screw-type extrusion and then injected into the mould where it undergoes hardening.

Ineach case hardening occurs without generation of gaseous by-products.

The resulting moulded articles have a great dimensional stability at elevated temperature, exceptionally low shrinkage values, and excellent electrical properties which remain unchanged under different environmental conditions.

The said moulded articles possess, moreover, good mechanical characteristics, very good resistance to chemical reagents, a low water absorption and can easily be coloured.

In particular, the said moulded articles possess electrical characteristics similar to those of conventional products used for the purpose, such as glass and ceramics, bm/ the saidcharacteristics being distinctly superior to those of products manufactured from thermosetting resi-ns such as phenol, urea and melamine resins, and also to those manufactured from the usual thermoplastic resins.

The manufactured articles of the present invention, moreover, show distortion temperatures under load (Martens degree) clearly superior to those made from the conventional thermoplastic resins.

In conclusion, the moulded articles of the present invention possess a whole collection of characteristics such as to render them useful in a wide range of applications and particularly for the construction of electrical and electronic equipment parts, such as: reels for coils, boxes for low and medium tension switches, insulators in general, connector blocks, fairleads, terminals, "handles, insulating supports and fans for electric motors.

Example 1 Preparation of the unsaturated polyester A Into a flask fitted with an agitator there are fed 264.4 parts by weight of 2,2'-bis(4-hydroxycyclohexyl) propane and '116 parts by weight of fumaric acid, the molar ratio between the two reagents being thus equal to i.I:I.

A current of nitrogen is caused to flow over the surface and the reagents are melted by heating to 170°- 180°C. They•are then heated to 200-205°C, whilst the temperature is maintained at the swan neck at about 105°C.

The said temperatures are maintained until an aæid value of the order of 40-50 is reache o A subatmospherìc pressure (20 mm Hg) is then applied and the temperature is maintained at 200-205°C ùntil an acid bml i0 value of the unsaturated polyester A of less than 20 is reached.

100 ppm of para-tert-butyl catechol are added and the mass is cooled and discharged.

The unsaturated polyester A thus obtained has the following characteristics:

- melting point - acid value - Gardner viscosity : 91°C : 17.6 : Z2 + 1/2 The melting point is determined at the capillary; the acid value is the number of milligrams of potassium hydroxide used to neutralize one gram of unsaturated polyester A; the Gardner viscosity is determined at 25°C in a 60% solution by weight of the unsaturated polyester A in styrene.

Example 2 Preparation of the unsaturated polyester B Operation is carried out according to the procedure of Example i, charging the flask with 166 parts by weight of isophthalic acid, 348.2 parts by weight of fumaric acid and 335 parts by weight of propylene glycol, the molar ratio between the reagents being thus equal to 1:3.0:4.4.

The resulting unsaturated polyester B has the fóllowing characteristics:

- melting point (at the capillary): 62-67°C - acid value (mg KOH/g): 17.8 -Gardner viscosity (at 25°C, in a 60% solution in styrene) :

X + i/3 Example 3 One prepares a moulding composition including the unsaturated polyesters A and B (whose Preparation has been bm/ l i0 Æ074038 described in Examples 1 and 2, respectively), and acrylamide.

The components of the composition are ndicated in Table i. In the said Table 1 the amounts of the components are given in parts by weight. Finally, the silica used is that known commercially as "Aerosil" The preparation of the composition is carried out in the following manner:

all the components, excepting the glass fibre, are fed into a ball mill and ground to a grain size of less than about 100 microns. Then the glass fibre is added and the mass is homogenized.

The homogenized mass is calenderede working under the following conditions:

- first roller temperature - second roller temperature - speed of the two rollers - working time - thickness of the sheet produced - 100°C : 85°C : 20 revolutions/minute : 2 minutes : 1 mm.

The sheets produced by calendering are ground in a hammer mill, having a net with a 5 mm mesh.

The characteristics of the resulting granulate are reported in Table 2.

As to the results of Table 2:

- the apparent density was determined in accordance with the DIN 53.468 standard; - the hardening time was determined by introducing the composition into a bowl shaped mould of the UNI 4272 type and putting it under a load of 5,000 kg., at a temperature of 150°C; the time in seconds elapsing between the closing of the mould and the formation of a bowl without surface bm/ l0 defects (blisters) defines tile hardening time; - the flow index was determined by introducing the composition into a bowl shaped mould of the UNI 4272 type, at the prefixed temperature of 150°C and applying a load of 5,800 kg by means of hydraulic press; at the instant at which the needle of the manometer, connected to the press, shows an increase in pressure, the chronometer is started; when the upper plane of the press has finished its descent, the chronometer is stopped; the intervening time, expressed in seconds, isthe flow index; - fluidity on a disc was determined by placing 50 grams of the composition at the centre of a disc-shaped mould, having a diameter of 32 cm and with 6 concentric circles drawn on the said mould; a pressure of 40,000 kg is applied for seconds, operating at 150°C; the speed of closing of the press is at 0.3 cm/second; the fluidity 0f the composition is expressed as the number of circles impressed on the disc; - packing was estimated by placing i00 grams of the compor sition in a 250 ml beaker with a 66 m inner diameter under a pressure of 15.1 g/cm2; after 45 days at 38°C the composition is sifted through sieves of 20, 40 and 50 mesh and the quantity of material remaining on each sieve as well as the consistency of the lumps is evaluated: the handling consistency of the lumps is exoressed by the words: non friable, a little friable, friable.

Under the moulding conditions, there are no adherences te the walls of the moulds, either chromium plated or not, and it is not necessary to lubricate the said moulds.

Test bars of the resulting granulate are moulded with dimensions 10x15x120 according to UNI standards.

i0 The moulding conditions are reported in Table 3.

The characteristics reported in Table 4, have been determined on the test pieces.

Examples 4 and One operates under the conditions of Example 3, using different amounts of acrylamidè and unsaturated polyesters A and B.

The results are reported in Tables 1 to 4.

Example 6 One operates as in Example 3 to prepare a moulding composition including the unsaturated polyester A and acrylamide.

The results are reported in Tables 1 to 4.

Examples 7 and 8 Operation is as in Example 6, the moulding pressure being varied.

The results are reported in Tables 1 to 4.

•able 1 Ex.3 Ex.4 Ex.5 Ex.6 to 8 Unsaturated polyester A 19.0 18.0 17 0 25.0 Unsaturated polyester B 7.0 6.0 5.0 - Acrylamide 1.0 3.0 5.0 2.0 Dicumyl peroxide 1.4 " 1.4 1.4 1.4 Zinc stearate 2.5 2.5 2.5 2.5 Silica 5.0 5.0 5.0 5.0 Calcium carbonate 14.1 14.1 14.1 14.1 Asbestos powder 20.0 20.0 20.0 20.0 Glass fibre (chopped strands) 30.0 30.0 30.0 30.0 bm/ w Table 2 Example 3 Apparent density (g/l) Hardenìng tì e at 150°C (sec) 120 Flow index at 150°C (sec) 8 Fluidity Ch a disc 7 1/2 Packing a little friable Example 4 7OO 7 3/4 a .little friable Example 7OO 1-2 a little friable E v nples 6-8 65O 9O a little friable i0 Stability in storage (months) ulding in chromium plated moulds building in nonchramed moulds Grain size 4000 (micron) 50O 25O i00 <I00 Table 3 no adherence no adherence 2-5% 60-63% 25-27% 5-7% 3-4% 3-4% no adherence no adherence 2-5% 60-63% 25-27% 5-7% 3-4% 3-4% no adherenoe no adherence 2-5% 60-63% 25-27% 5-7% 3-4% 3-4% no aæærenoe no adherence 2-5% 60-63% 25-27% 5-7% 3-4% 3-4% EX. 3 Tapera ture (°C) 160+2 Pressure (Kg/ n2) 200 Time (sec/n n of thickness) 90 Ex. 4 160+2 20O EX.

160+2 2OO EX.6 160+2 2OO 9O EX. 7 160+2 9O EX. 8 160+2 9O o Æ074038 Table 4 Bending strength (Kg/ n ) DIN 53452 Impact résistance 4.0 (Kg /on) DIN 53453 Impact resistance 3.0 wi notch (Kg.cm/ cm ) DIN 53453 Martens degree (°C) 147 DIN 53458 Shrinkage (%) 0.6 DIN 53464 Post-shrinkage (%) 0.08 DIN 53464 Water absorption (mg) DIN 53472 Surfaoe resistance1013 (ohm) DIN 53482 Volume resistance1014 (ohm/cm) DIN 53482 Dissipation factor 0.045 (tgõ) DIN 53483 Dielectric strength 5.5 (Kv/mm) DIN 53481 Tracking resistanoe KA2 « DIN 53480 Degree of incande2 soence (degree) DIN 53459 Ex. 3 Ex.4 Ex.5 Ex.6 Ex.7 Ex.8 545 595 610 500 500 500 4.3 4.5 4.4 4.4 4.5 3.0 3.0 3.2 3.2 3.2 150 154 140 140 140 0.6 0.6 0.6 0.6 0.6 0.08 0.08 0.05 0.05 0.05 101310 13 101410 14 6.1013 6.1014 6.1013 6.1014 6.1013 6.1014 0.045 0.045 0.029 0.029 0.029 5.5 5.5 5.1 5.1 5.1 KA2 KA2 KA2 KA2 KA2 • v k % "e ' Æ074038 THE EMBODIMENTS OF THE INVENTION IN WHICll AN EXCLUSIVE