DE2064268A1 - Manufacture of thermosetting novolak molding compounds with increased thermal resistance - Google Patents

Description

Troisdorf, December 24, 1970 70 158 (1861)

DYNAMIT NOBEL AKTIENGESELLSCHAFT Troisdorf, District Cologne

"Production of thermosetting novolak molding compounds with increased

thermal resistance "

The present invention relates to the use of metaboric acid and / or boron oxide for the production of thermosetting Novolak molding compounds with increased thermal resistance under plasticizing conditions.

As is well known, molding compounds based on novolaks belong to the thermoset materials. Under novolaks are included Phenol-formaldehyde condensation products understood in the presence of formaldehyde-releasing compounds, preferably Hexamethylenetetramine, are thermosetting.

The processing of thermosetting masses into solid molded parts is known to be done in such a way that the masses are first converted into a plastic, viscous state under the influence of heat, then deformed and compressed under the influence of pressure in a suitable mold and there under the conditions in V. / ool prevailing elevated Temperature at a formative solid plastic articles irreversible off ": ur, ^h: irten.

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The modern thermoset processing machines include the pressing and transfer molding machines, in which the masses in front of their Entry into the hot tool either in continuously working Piston or screw plasticizing units pre-tempered or in pelletized form are subjected to an automatically controlled high-frequency preheating. Furthermore are Piston and screw injection molding machines are known in which the masses are continuously and evenly preheated in the plasticizing room and then injected into the higher heated tool under pressure and cured there.

The curing time, which affects the overall cycle of bulk processing is known to have a decisive effect on the type of mass used in terms of its flow-hardening behavior determined as a function of the temperature.

Experience has shown that such thermoset molding compositions are particularly suitable for the processing methods mentioned that are can easily be converted into a relatively low-viscosity state under the usual preheating conditions, with relatively low injection pressures and short injection times can be injected into the tool and those used for phenolic compounds Mold temperatures show rapid cure.

Essentially, these thermosetting molding compositions are required to be in their pre-placed state under preheating conditions due to a sufficient thermal resistance their low viscosity and thus

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their good flow and spray properties during the plasticizing process maintained without premature hardening phenomena occurring. Such mass behavior largely protects the The processing machine and its tools protect against wear and tear and ensure a high level of operational reliability during the processing process. There is also the requirement that these molding compounds after reaching the mold temperatures harden quickly.

In addition, those molding compositions deserve preferred interest because of their mentioned thermal resistance in the plasticized state an increased preheatability is given is. The increased mass preheating that both through Use of increased plasticizing temperatures as well as the generation of increased frictional heat when the plasticized material flows Mass is achieved through appropriately narrowly dimensioned sprue bars within transfer molding and injection molding tools, It is known that this leads to a significant shortening of the processing cycle and to molded parts of the best quality. Thermoset Molding compounds that on the one hand have increased thermal stability and good flow properties in their plasticized Experience shows that show the condition under preheating conditions and, on the other hand, are quick-curing at mold temperatures a significant increase in performance in the production of high quality molded parts.

It is already known that the processing properties mentioned such thermosetting novolak molding compounds do justice

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those that contain the hexamethylenetetramine used for novolak hardening not in free form, but as a metaboric acid compound in which the two components are in a molar ratio of 1 ι 1. In this case, the increase in the thermal stability of the novolak-based molding compositions under preheating and plasticizing conditions is achieved in that the hexamethylenetetramine is in the form of a sufficiently thermally stable compound that only converts the hexamethylenetetramine under the action of the usual mold temperatures ^{of 160 to 190 ° C.} Mass hardening releases completely. In these compositions, the decrease in the flowability and the insertion are even with the increased preheating or Piastiziertemperaturen of 110 to 120 ⁰ C a premature curing reaction is delayed compared with the usual hexamethylentetraminhaltigen novolac molding compounds, whose flowability in general even at 90 to 100 ° C as a result the beginning of hardening decreases noticeably.

The disadvantage of this method is the need for separate Production of hexamethylenetetramine monometaborate, which is known to be produced by the dry reaction of hexamethylenetetramine and orthoboric acid is created »The quantitative conversion of the starting substances, the proper drying of the reaction product to remove the water of reaction and the high The degree of fineness of the salt produced is essential for its use and optimal effect as a raw material in novolak molding compounds an absolute prerequisite for the use of the reaction product for the desired purpose.

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Another method is to avoid the separate production of dry and finely powdered hexamethylenetetramine monoinetaborate known according to which this salt is formed during the manufacture of novolak molding compounds. In this procedure will be the raw materials hexamethylenetetramine and orthoboric acid to the novolak molding compound added in equimolar proportions and the batches under certain process conditions processed so that the hexamethylenetetramine monometaborate is formed during the manufacturing process.

This process has the disadvantage that the mass preparations containing orthoboric acid are used in the process of their preparation to form the final molding compound product Experience has shown that production times are prolonged, leading to the extensive formation of hexamethylenetetramine monometaborate and are necessary to remove the released water of reaction. Furthermore, in this procedure the implementation of hexamethylenetetramine and orthoboric acid generally cannot be achieved quantitatively, so that these mass-produced products are lower under plasticizing conditions Thermal resistance is shown by those molding compounds that contain the defined hexamethylenetetramine-metaboric acid compound in their batch mixture from the start included as raw material.

Said two methods is also attributable to that the temperatures of the rolling rolls must be below about 12O ⁰ C in the preparation of the mass approaches in the usual manner running with friction roller units, otherwise due to increased rolled sheet temperatures employed or forming

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Hexamethylenetetramine metaborate with the release of the ethylene tetramine begins to decompose. Show because of the necessary compliance with relatively low rolling temperatures both of these methods suffer from reduced manufacturing efficiency of novolak molding compounds.

It has now been found, surprisingly, that one can use metaboric acid and / or boron trioxide for the production of thermosetting novolak molding compounds where hardening is greatly delayed under plasticizing conditions, but under tool conditions is accelerated. Novolak molding compositions produced using these compounds show the disadvantages of those previously known Novolak molding compounds no longer.

The use of boron oxide in the production of novolak molding compounds has been known for a long time. Thus, in British patent specification 622 332, a process is described to produce novolak molding compounds that cure quickly under mold conditions and are easy to demold in the cured state Add salt © to the novolak. All the substances mentioned in this specification cause the mass 160 to 180 ⁰ C with good flowability shows rapid curing "The optimum balance between the mutually acting forces fluidity - curing best achieved by Orthoborsäure- at 160 Ms 180 ^and C '

In contrast to the novolak molding compounds mentioned in the British patent, the molding compounds produced according to the invention are much more thermally stable in the plasticized state (110 to 135 ° C), maintain their high flowability over a longer period of time and only harden after flowing into the 160 to 180 degrees ⁰ C heated molding chamber. For novolak molding compositions which meet these requirements, only metaboric acid and / or boron trioxide can be used of the compounds mentioned there; all other compounds mentioned are poorly or not at all suitable for this purpose.

According to the invention, metaboric acid is added to the molding compositions in amounts of 0.5 to 20% by weight, preferably 1 to 12% by weight, based on the Solid resin content, added. The proportion of boron trioxide is between 0.5 and 15% by weight, preferably between 1 and 10% by weight, based on the solid resin content.

Novolak molding compounds generally consist of 35 to 55% by weight of resin (condensation product of phenols and formaldehyde), 60 to 40% by weight of fillers of an organic and / or inorganic type as well as hexamethylenetetramine and small amounts of lubricants, Dyes, pigments and 1 to 2.5% by weight of alkaline earth oxides.

The weight ratio of novolak to hexamethylenetetramine in the molding compound can vary between 100: 12 and 18; preferably it is between 100: 15 and 100: 17. Instead of hexamethylenetetramine, other formaldehyde-releasing compounds can also be used . Connections are used.

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The fillers include wood flour, cellulose, fibers and chips of organic tissue, paper fibers, asbestos, mica, Fluorspar and rock flour.

The lubricants are added to the novolak in amounts of 0.5 to 2.0 wt.96. They encompass everyone in the making of Novolak molding compounds known lubricants, such as zinc, calcium or magnesium stearate or stearic acid.

As is known, to produce the novolak molding compounds, the additives are mixed with the resin and compacted while hot, preferably by means of rolling units. The roller head that forms in this process is removed from the roller after a certain period of rolling separated and, after cooling, ground to granules.

According to the invention, metaboric acid or the boron trioxide added in the specified amounts. However, it is also possible to use the boron compounds mentioned as a premix to be added to the main mixture with some of the aggregates and then compacted while hot.

These mass approaches lead to highly plastic rolled sheets when they are hot-compacted by means of rollers. The good thermal stability of the compacted masses demonstrated by the fact "that di © WaIz- £ skins after their cooling, grinding UNCT provide a granular welpheövim plastischen.Zustand; improved heat resistance

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below the usual preheating and plasticizing temperatures and characterized by increased flow and splash properties is.

Opposite the use of metaboric acid and / or boron trioxide Orthoboric acid has the advantage that the batches can be worked up more easily and more quickly to give novolak molding compounds. In the As described above, hot compaction of mass formulations containing orthoboric acid requires extended rolling times in order to to allow the above-mentioned conversion of orthoboric acid and hexamethylenetetra- "min to run off to metaborate and that which is released in the process To largely remove water of reaction from the bulk goods. In contrast, this water of reaction forms during use of metaboric acid or boron trioxide, so that the hot compression of the metaboric acid or boron trioxide-containing mass approaches is to be carried out in shorter times.

As a further advantage, it has surprisingly been found that the mass approaches with metaboric acid or boron trioxide with respect to those similar can be compacted hot with orthoboric acid, even at the elevated temperatures of from about 120 to 140 ⁰ C and still result in molding compositions which comprise at. their processing unrestrictedly show the advantages mentioned in terms of thermal and flow behavior. As already described, these increased compression temperatures cannot be used in the preparation of cash registers containing orthoboric acid, since under this temperature load the metaborate formed primarily from orthoboric acid and hexamethylenetetramine with elimination of water

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begins to decompose with the consequence that the resulting Novolak molding compounds no longer have the desired thermal stability in the plastic state when they are processed. the surprising finding that the thermal stability of metaboric acid or novolak molding compounds containing boron trioxide If the increased compression temperatures persist, it can be concluded that the increased thermal resistance of the molding compositions according to the invention do not depend on the formation of hexamethylenetetramine metaborate but is due to a different chemistry.

During their processing, the novolak molding compositions can be mixed with the additions of metaboric acid or boron trioxide according to the present invention Invention easily in the plastic state of relatively low viscosity under the usual preheating conditions convict. At the plasticizing temperatures, the masses retain their good properties due to their increased thermal resistance Flowability and sprayability over a longer period of time, so that greater operational reliability in the processing of preplasticized thermosetting novolak molding compounds is guaranteed. At the hardening temperatures customary for phenolic compounds Above about 155 ° C, the compounds quickly harden to form a solid and bubble-free molded part.

The metaboric acid recommended as "raw material in novolak molding compounds" is produced, as is well known, by heating the orthoborsaem * © within the temperature range of about 70 Ms 150 ⁰ G with elimination of water. At temperatures above 150 ⁰ G, the metaboric acid is converted into boron trioxide ",

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example 1

Eight mixtures of novolak molding compounds in the usual composition with increasing amounts of metaboric acid were prepared in accordance with the information in Table 1. The boric acid was added as a premix with some of the additives to the other components of the batch and mixed in. This approach blends were in a known manner by a roll aggregate was heated in which, with a friction of 19/23 to a platen roller to 9O ° C, the other roller at 7O ° C λ, with a rolling time of 2.5 min compacted.. The rolled pelts showed good plastic behavior and were ground to granules after they had cooled down.

To test the flowability at mold temperatures, the granulate masses obtained were in the form of tablets of 9 × 6 mm Diameter and 11.5 mm height at a temperature of 165 ° C

and a pressure of 48 kp / cm in a flow channel of 3.2 μ Diameter pressed; the length of the flow stick produced during mass hardening (in min) was used as a measure of the flow * determined by the capacity of the bulk samples. The extrusion tester from Zwick was used to carry out these measurements.

To test the thermal resistance of the masses under PIa-, stizierbedingungen the individual mass samples were on a. brought temperature of 110 ⁰ C and depending on the duration of the temperature exposure again subjected to the aforementioned flow test in the Zwick device using a pressure of 72 kp / cm. The test results are shown in Table 1. ₁₂ _

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In order to characterize their flow behavior, the individual bulk samples were examined in test quantities of 20 g in the Brabender plastograph. To this end, the used kneading chamber "Plasti-Corder MB 30" was heated to 115 ⁰ C. The rotating speed of the driven kneading drum was 30 rpm. Firstly, the minimum torque was measured as a quantity proportional to the viscosity of the plasticized mass and, secondly, the dwell time of the mass in the plastic state as a measure of its thermal stability.

As can be seen from the test results compiled in Table 1, novolak molding compounds with the addition of metaboric acid show an increased resistance of their flowability in the plastic state compared to mass preparations free of metaboric acid. This manifests itself in the fact that the metaborsäurehaltigen molding compositions, first - according to the measurements in the flow tester - their good flowability maintained on prolonged exposure duration of the increased plasticizing von.11O ⁰ C and secondly - attain lower minimum values of the torque and in - according to the test results of the Brabender plastograph Their low-viscosity, plastic state allow longer dwell times compared to the conventional, metaboric acid-free novolak molding compounds.

Example 2

Using boron trioxide mixture eight approaches V0 n were novolac molding compounds prepared in the composition shown in Table 2 & aftaL g Example-1 "on roller unit ©, as in the ^example; 1 described, Verdle & tfc-fcj vsuaa the cooled Walsfel-Ie to a granulate, grind.

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Under the test conditions given in Example 1, these were Mass samples examined in terms of their storage time under the plasticizing temperature in the Zwick test device and the torque-time function is determined in the Brabender plastograph.

Similar to the test results given in Example 1 for metaboric acid-containing novolak molding compounds, this also improves Boron trioxide instead of metaboric acid, within a certain proportion, influences the flow behavior of the novolak molding compounds under plasticizing conditions, as can be seen from the measured values compiled in Table 2.

Example 3

The mixture formulation with 2.1% by weight of metaboric acid mentioned in Example 1 and the mixture formulation with 1.7 % by weight of boron trioxide mentioned in Example 2 were compacted at the increased rolling temperatures of 135.degree. C./85.degree. After a rolling time of 2.5 minutes, plastic pelts were pulled off the roller and, after they had cooled, ground to form granules.

Despite the increased roller temperatures used, the two granulate masses maintain their good thermal stability during the investigated exposure time of the plasticizing temperature of 110 ° C, while those novolak molding masses that do not contain these additives according to the invention or instead contain orthoboric acid in an equimolar proportion to the hexamethylenetetramine content, which gives the best results , when using the

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high rolling temperatures suffer severe losses in their flowability below the plasticizing temperature. Table 3 shows the comparison of the measured values.

Example 4

333 parts of novolak were made with 540 parts of asbestos flour, 57 parts Hexamethylenetetramine, 13 parts of metaboric acid, 15 parts of magnesium oxide, 15 parts of zinc stearate and 27 parts of color additives are intimately mixed. The mixture was heated to 120.degree. C./80.degree Rolling rolled for 2.5 minutes. After cooling, the rolled sheet obtained was ground to give granules.

A mixture was prepared in the same way, consisting of 333 parts of Növolak, 543 parts of asbestos flour, 57 Parts of hexamethylenetetramine, 10 parts of boron trioxide, 15 parts of magnesium oxide, 15 parts of zinc stearate and 27 parts of color additives.

"Parts" are to be understood as meaning parts by weight.

Both asbestos-filled masses showed an extremely stable flow behavior under plasticizing conditions. Even after four hours of exposure duration of Piastiziertemperatur of 110 ⁰ C flow tester Zwick were gemessenj under the test conditions mentioned in Example 1 high flow path lengths of the two masses in the in the range of 60 to 65 mm

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Table 1:

The improvement of the flow resistance of novolak molding compounds at plasticizing temperatures by adding metaboric acid.

Mixing approaches of novolak molding compounds

Solid resin (%) hexamethylene '

tetramine %

Metaboric acid %

Wood flour %

Magnesium oxide %

Zinc stearate %

Asbestos flour %

Color %)

40.0 6.8

41.5 41.5

O, b 40.9

1.1 40.4

39.4 58.9

3.2 4.3 38.3 37.2

2.0 1.0 6.0 2.7

Warm storage time (hours)

Flow path length (mm) of the novolak molding compounds depending on their storage time

110 ⁰ C

0 72 72 750 750 73 73 71 70 700 700 650 63 62 1 56 60 62 65 69 71 66 65 2 47 49 53 56 65 64 62 57 3 40 41 46 54 58 59 59 53 4th 36 .37 43 49 51 44 44 43 Flow behavior of the Masses in Brabender plastographs (Chamber temperature 115 ° C) Minimal twist moment (mp) 700 650 500

Dwell time (min.) Of the mass in the plastic state up to a torque of 2500 mp 11.8

11.8 13.8 15.3 18.5 19.5 21.0 18.5

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Table 2:

The improvement of the flow resistance of novolak molding compounds at plasticizing temperatures by adding boron trioxide

Mixing approaches of novolak molding compounds

Solid resin (%) Hexamethylenetetramine % Boron trioxide % Wood flour % Magnesium oxide % Zinc stearate % Asbestos flour% Color %

40.0 6.8

0/4 0.8 1.3 1.7 271 41.1 40.7 40.2 39.8 39.4

2.6 3.4 38.9 38.1

2.0 1.0 6.0 2.7

Warm storage time Flow path length (mm) of the novolak molding compounds (hours) depending on their storage time at

110 ⁰ C.

0 72 750 73 72 71 74 73 72 Brabender plastographs 650 650 • 650 64 1 56 64 67 68 71 70 71 650 60 2 47 55 58 61 68 67 66 53 3 40 49 54 56 62 60 53 650 48 4th 36 42 46 52 54 52 45 38 Flow behavior of May ssen im (Chamber temperature 115 ⁵ C) Minimal twist moment (mp) 700 800

Dwell time (min.) Of the mass in the plastic state up to a torque from 2500 mp 11.8 * 13.4 14.8 17.2 19.6 20.5 21.0 18.3

ORfGlNAL INSPECTED

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Table 3'- Influence of the rolling temperatures

Mixing approaches of novolak molding compounds

Solid resin {%) hexamethylenetetramine % metaboric acid % boron trioxide % orthoboric acid % wood flour % magnesium oxide % zinc stearate % asbestos flour % paint %

40.0 6.8

Έ7Τ

1.7 ίο

3.0 S8.5

41.5

271
~ A.

1.7 -

3.0 -. .5 41. 5

Rolling temperatures ° C / ° C

90/70

135/85

Warm storage time Flow path length (mm) of the novolak molding compounds in (Hours) depending on their storage tent

11O ⁰ C

O 71 74 71 72 70 72 66 63 1 69 71 68 56 68 67 54 49 2 65 68 59 47 62 63 36 32 3 58 62 51 40 56 54 23 mm 4th 51 · 54 43 36 48 45

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Claims (3)

- 18 claims 1. Use of metaboric acid and / or boron oxide for production of thermosetting novolak molding compounds, in which the hardening is greatly delayed under plasticizing conditions, under mold conditions however is accelerated. 2. Use of metaboric acid for the production of thermosetting Novolak molding compositions according to Claim 1, characterized in that that the metaboric acid in amounts of 0.5 to 20% by weight, preferably 1 to 12% by weight, based on the solid resin content, used. 3. Use of boron oxide for the production of thermosetting novolak molding compositions according to claim 1, characterized in that the boron oxide is used in amounts of 0.5 to 15% by weight, preferably 1 to 10% by weight , based on the solid resin content. Dr, Sk / Ko 209129/0810