DE3021213A1 - REDUCING VISCOSITY IN FILLER RESIN SYSTEMS - Google Patents

Description

Reduction of viscosity in resin systems containing fillers

The invention relates to inorganic fillers commonly used in various resin systems, especially ground lime fillers suitable for use in polymerizable resin compositions including such materials as styrene-containing polyester resin, epoxy resin and linseed oil are suitable. The invention also relates on a method to increase the pot life and Reduction of the binder requirement for ground lime filler.

The binder requirement is generally expressed as the amount of Binder or resin, which is required to achieve the viscosity given for the production of a resin / filler mixture to completely moisten the filler used. The pot life, on the other hand, is the length of time between Mixing the binder or resin and filler and the time, to which the mixture has become viscous in order to be processed further.

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Thermosetting and thermoplastic resin composition based products usually contain a substantial amount Filler content. The commonly used fillers are much cheaper than the associated resin systems. Thus there is a strong incentive to increase the filler content up to a maximum consistent with the required strength of the cured product. In many systems the optimal filler content cannot be achieved because the resin / filler mixture becomes too viscous to process to become before the optimum can be achieved. Therefore, there is a constant search for methods of reducing the binding agent as needed.

In the case of resins with a high content of fillers, the pot life is often reduced to such an extent that the time required for further processing, such as humidifying fiberglass reinforcement or releasing trapped air, is not sufficient.

Previous attempts to solve the above problems included Solutions such as changing the particle size distribution of the filler, surface abrasion, Kömpaktieren and Surface coating of the filler. These attempts met with varying degrees of success. An attempt to achieve a better distribution of the filler is disclosed in published Japanese patent application 50/40399. In this Publication is the coating of particles, among other things Calcium carbonate with various organic acids, e.g. also chlorobenzoic acid, is described. But there is an increased pot life and reduced binder requirements are desirable.

The object of the invention is primarily an economical process to achieve a low binder requirement and increased pot life for those commonly used ground lime fillers, e.g. calcite and dolomite lime.

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The invention is based on the finding that a filler with ground limestone coated with 0.05 to 0.50 percent by weight benzoic acid, with an average diameter of the ground limestone of about 0.25 µm to about 44 µm for increased pot life and decreased Binder demand leads in an economical manner. Preferred forms of ground limestone include calcitic and calcite dolomitic lime. Preferred binders include styrenated polyester resins, epoxy resins and linseed oil.

The essence of the invention is the finding that particles of ground lime coated with benzoic acid have the initial viscosity of resin / filler mixtures and the development such a high viscosity that the mixture can no longer be processed. Lower initial viscosity with the same filler content means less binder requirement. A delay in the development of too high a viscosity is called the increased pot life. The two effects are related to one another in that they have a lower initial viscosity due to the longer time required for increased resin polymerization to achieve a larger change in viscosity from a lower starting point to the same final viscosity of the unprocessability, usually to one long pot life. According to the invention, the initial rate of viscosity development is also reduced. Therefore the pot life is extended even beyond that expected from a reduced initial viscosity.

Coating of the selected particle size of the ground limestone can be accomplished in a number of known ways. The preferred technique, however, is dry blending benzoic acid with the ground limestone by intensive means rotating and pushing stirring at peripheral stirrer speeds of, for example, 20 to 60 m / s. With this kind of in-

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intensive mixing, the friction increases the temperature of the batch. In general, such a mixing is sufficient for 10 to 20 minutes and leads to a filler ^{temperature of at least 120 °} C., unless the mixer is specially cooled.

One area in which the invention is particularly applicable is the assembly of glass fiber reinforced panels and panels Mass molding compounds. A typical plate dimensions would be as follows Composition:

Components parts

Low shrinkage polyester resin 100

t-butyl perbenzoate (catalyst) 1

Magnesium hydroxide (additive for ripening control) 4

Zinc stearate (mold release agent) 5

Benzoic acid-coated, ground

Lime (filler) 150

The above mixture of ingredients (72 percent by weight) is covered with cut glass fibers (28 percent by weight). The web formed is compressed between polyethylene films by rollers, taken up and matured at about 30 C until the viscosity rises to over about 20 χ 10 Pa · s (20 χ 10 cP). This usually takes 1 to 2 days. The matured railway can
the.

can then be compression-deformed to their final shape ^{at about 150 0 C}

The invention is further illustrated by the following examples, which are for the purpose of illustration only, while the invention is defined by the claims.

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example 1

Six samples of milled limestone were made with various Proportions of benzoic acid coated by the preferred method of intensive dry mixing. A seventh rehearsal was made treated identically, but without benzoic acid (as a control). Each sample was prepared as follows, using only the amount of benzoic acid was varied for each different sample.

A 1000 g amount of ground limestone with an average Ball diameter of 5.5 µm (Pfizer Inc.'s Vicron 25-11) was placed in an intensive mixer, Model 2 JSS Prodex-Henschel. The desired proportion of benzoic acid was added, e.g., 2 g, to make a 0.2% benzoic acid coated product. Then the batch was 10 min stirred at 3800 rpm (speed of the blade tip 42 m / s).

Portions from each sample were used to prepare representative plaque-resin-filler blends. A total of 240 g of resin (Paraplex P-19D from Rohm & Haas) were weighed into a 600 ml beaker. This resin is a mixture of isophthalic acid-based polyester and a thermoplastic polymer (as disclosed in US Pat. No. 3,701,748) in styrene solution. Then 360 grams of a coated lime filler was added. This ratio of resin plus filler is referred to as 60% filler content or 150 parts per 100 parts resin (150 phr). This mixture was stirred immediately? until complete distribution was achieved. The stirring caused the temperature to rise to 29 ⁰ C (85 ⁰ F), to a temperature at which the viscosities were measured.

A Brookfield viscometer, model HBT, equipped with a Spindle # 6, was used to measure viscosity at 5 rpm. For the measurement, the spindle was first inserted into the sample

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28.8 (28 800) 20.8 (20 800) 16.0 (16 000) 19.2 (19 200) 20.8 (20 800) 24.0 (24 000) 25.6 (25 600)

Immersed to the spindle knot and then attached to the viscometer. The viscometer was turned on at 5 rpm and a reading was taken at the second revolution. The viscosity in centipoise corresponds to the reading multiplied by 16,000. The results are tabulated below :

% By weight benzoic acid on lime: initial viscosity 10 min dry mixed Pa s (cP)

0.10

0.20

0.25

0.30

0.35

0.50

These data show that a considerable reduction in viscosity can be achieved by adding benzoic acid down to 0.10% can. Economic considerations give little incentive to add more than 0.5% benzoic acid.

Example 2

Example 1 shows the maximum influence of the overdraft at about 0.2% benzoic acid. This coating value was repeated but using a coating solution in place of the Dry method of Example 1. A batch of 1500 g milled Limestone (Vicron 25-11) was poured into a Patterson-Kelley V-cone mixer, Model LLB-7754 brought with an intensive stir bar rotating at 1725 rpm. A solution of 3.0 g Benzoic acid in 8.0 ml of ethanol was added. This mixture was mixed for 6 hours to thoroughly distribute the acid and to evaporate the ethanol. The result was a limestone particle filler coated with 0.20% benzoic acid. A pro

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The coated filler and uncoated lime were added to resin as in Example 1 and the initial viscosity certainly. The results were as follows:

% By weight of benzoic acid with initial viscosity using a coating solution Pa s (cP)

O 50.0 (50 00Q)

0.20 38.2 (38 200)

Example 3

The presence of benzoic acid leads to extended pot life of resin / filler mixtures, as shown in this example. Representative film or sheet molding compound resin / filler mixtures were made up as follows: A batch of 240 g of the resin of Example 1 (Paraplex P-19D) was placed in a 600 ml beaker. 360 g of lime filler, 12 g of zinc stearate and 2.4 g of t-butyl perbenzoate were added with stirring. The temperature of the mixture was brought to about 30 ° C by the influence of mixing, and 9.6 g of magnesium hydroxide was added as a ripening / thickening agent. Stirring was continued and the temperature increased to about 32 ⁰ C. The mixture was poured into a can about 1/2 liter (1 pint) and the viscosity measured after various times according to the procedure of Example 1.

Four different lime fillers were tested, one ground Limestone with an average round diameter of 3.5 µm (H.T. Campbell & Sons Co.'s Camel-White), as well Mixtures of Camel-White with a 0.50% benzoic acid-coated ground lime (Vicron 25-11), prepared according to the procedure described in Example 1. The results were as follows:

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filler

Total weight -% benzoic acid

100% Camel-White, 0% Coated Vicron (control test)

75% Camel-White, 25% Coated Vicron

50% Canel-White, 50% Coated Vicron

25% Canel-White, 75% Coated Vicron

0.125 0.250

0.375

Viscosity in Pa-s (cP) according to

0 min 5 min 30 min 60 min

30.4 30.4 52.8 73.6

(30400) (30400) (52800) (73600)

27.2 27.2 33.6 51.2

(27200) (27200) (33600) (51200)

28.8 27.2 28.8 40.0

(28800) (27200) (28800) (40000)

25.6 27.2 27.2 40.0

(25600) (27200) (27200) (40000)

Example 4

Benzoic acid was found to lower the initial viscosity a sheet or sheet molding compound when used with ground calcitic and dolomitic limestone was used. Samples of these fillers were applied using the method of Example 1 as a dry coating. they were then compiled according to the method of Example 1 and measured the initial viscosity. The control samples without coating were agitated in the Henschel mixer for the same time (10 min) as the coated samples. The results were as follows:

filler

% By weight of initial benzoic acid as excess viscosity,

Mass avg.
Particle size
(μη) surface
(m ² / g) train on the
filler
• Pa «s (cP) Calcitic 5.5
lime
(Vicron 25-11) 2.8 0
0.20 28.8 (28800)
16.0 (16000) Calcitic 8.0
lime
(Vicron 31-6 1.6 0
0.11 25.6 (25600)
16.0 (16000) Calcitic 7.0
lime
(Vicron 41-8) 2.2 0
0.16 19.2 (19200)
11.2 (11200) Dolamitiscber 10.0
lime
(Dolocrori 32-15) 1.2 0
0.085 28.8 (28800)
20.8 (20800)

Note: Vicron and Dolocron are trademarks of Pfizer Inc. for special grinds calcitic or ground dolomitic limestone.

Example 5

A sample of ground lime filler (Vicron 25-11) was coated with 0.2% by weight benzoic acid according to the method of Example 1, with the exception that it was stirred intensively for 15 minutes and the temperature rise of the batch was not controlled. The final temperature of the coated product was 145 C. The uncoated control sample rose to 190 ^° C. during the same 15 min of stirring. Portions of these two filler compounds were used to make resin / filler mixtures with two different

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those resins by following the procedure of Example 1 (which used a styrene-containing polyester resin). the Initial viscosities were measured with the following products:

resin filler % Filler content ^
phr initial viscosity
Pa-s (cP) 7.36 (7360)
3.25 (3250) linseed oil non-coated
Q, 2% benzoic acid 67
67 200
200 8.32 (8320)
6.08 (6080) Epoxy non-coated
0.2% benzoic acid 60
60 150
150 'v "\ r * \ tr τ τ t-Λ TS " v ^ r? Ύΐτί τ ^ - ^ \ τ Ύ * \ / ~ \ rm Annotation: L- * τ> * \ m * ~ ι ^ 4 τ '& - * r ^ τ f ~ < v * + - ** ^ r *

Epoxy equivalent of 178-186 and 12% reactive diluent content (Genepoxy MI80 der General Mills).

Viscosity measured with a # 4 spindle.

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Claims (6)

P.C. 6141 patent claims 1. Filler made from ground limestone, coated with .0.05 to 0.50 wt .-% benzoic acid, with an average Diameters from about 0.25 µm to about 44 µm. 2. Filler according to claim 1, the ground limestone of which is calcitic limestone. 3. Filler according to claim 1, the ground limestone of which is dolomitic limestone. 4. Agent containing the filler according to one of the preceding claims in admixture with a styrenated one Polyester resin. 5. Agent containing the filler according to one of claims 1 to 3 in a mixture with an epoxy resin. 6. Agent containing the filler according to any one of claims 1 to 3 mixed with linseed oil. 030050/0927 ORIGINAL INSPECTED