WO2006089575A1

WO2006089575A1 - Flow properties for polyphenilene oxide melts while a second processing

Info

Publication number: WO2006089575A1
Application number: PCT/EP2005/013209
Authority: WO
Inventors: Jonas Scherble; Christoph Krohmer; Hans-Gerhard Fritz; Fan Jin
Original assignee: Röhm Gmbh
Priority date: 2005-02-23
Filing date: 2005-12-09
Publication date: 2006-08-31
Also published as: DE102005008552A1

Abstract

The invention relates to a method for low linking polyphenilene oxides or polyphenilene ethers (PPO) consisting in extruding or kneading PPO-containing moulding materials.

Description

Flow behavior of polyphenylene oxide melts during processing Il

The invention relates to a process for the easy crosslinking of polyphenylene oxides or polyphenylene ethers (PPO) in the extrusion or in the kneading of PPO molding compositions.

The polyphenylene ethers that are useful in these formulations include a variety of structural units of the general formula

wherein in each of these units independently each Q1 is independently halogen, primary or secondary lower alkyl (i.e. alkyl of up to 7 carbon atoms, phenol, haloalkyl, aminoalkyl, hydrocarbonoxy or halohydrocarbonoxy, with at least 2 carbon atoms separating the halogen and oxygen atoms and each Q2 independently from each other is hydrogen, halogen, primary or secondary lower alkyl with the meanings given below, phenyl, haloalkyl, hydrocarbonoxy or halohydrocarbonoxy, as defined for Q1.

Examples of suitable primary lower alkyl groups are methyl, ethyl, n-propyl, n-butyl, isobutyl, n-amyl, isoamyl, 2-methylbutyl, n-hexyl, 2,3- or 4-methylpentyl and the corresponding heptyl groups. Examples of secondary lower alkyl groups are isopropyl, sec-butyl and 3-pentyl. All alkyl radicals are preferably straight-chain rather than branched. Most common is any Q1 alkyl or phenyl, especially C1-4 alkyl and each Q2 is hydrogen. Suitable polyphenylene ethers and their preparations are described in a large number of patents (for example DE41 279 78, EP226 149, JP07026018, EP133 657, JP51027702).

“PPO-based molding compositions” or “PPO molding compositions” are understood below to mean preparations which consist of at least 40% by weight, preferably at least 60% by weight and particularly preferably at least 75% by weight, of the polyphenylene ethers described above.

It is known from the literature that hydrogen atoms in the benzyl position on aromatic rings can be abstracted particularly easily by radicals. The resulting benzyl radicals can react further with suitable reagents (Streitwieser / Heathcock: Organic Chemistry, VCH Weinheim). This enables chlorination and bromination or the addition of unsaturated compounds.

If polymers containing hydrogen benzyl are treated with radicals, e.g. The decomposition of peroxides results in the formation of benzyl radicals on the polymer chains. These radicals can recombine and cross-link polymer chains (e.g. Ghaoui, L .; Shanfield, H. Zlatkis, A., Chromatographia (1984), 18 (1), 11-14). The addition of styrene leads to graft copolymers (US4483958).

If larger amounts, ie more than 10% based on the total mass of polyunsaturated compounds such as triallyl isocyanurate (TAIC), are used, this leads to strong crosslinking, including the starting polymer. The formulation of (modified) poly (2,6-dimethyl-1,4-phenylene) oxide with large amounts of TAIC and peroxides is described in several patent applications (for example WO2003 / 033566, WO2002 / 018493, JP2000297165). Similar formulations are based on the crosslinking agents 4,4'-dimaleiimidodiphenylmethane (JP63049694, DE3207260) or 005/013209

a maleimide functionalized aniline-formaldehyde copolymer (JP01053298). By curing these formulations, highly cross-linked, infusible thermosetting plates are obtained which are used in copper-clad form as printed circuit boards for electrical circuits.

Further examples of formulations for printed circuit boards are based on PPO, which was equipped with reactive groups in an upstream process step. E.g. PPO can be functionalized with allyl groups and then copolymerized with triallyl cyanurate and / or triallyl isocyanurate (e.g. JP03045650, JP04091223). The functionalization of PPO takes place either already during the synthesis by copolymerization of suitable monomers, e.g. of 2-allyl-6-methylphenol (US 3,422,062) or far more often in a separate modification step in solution or in the molten polymer. An example of the modification in solution is the nitration of PPO in chloroform and subsequent reduction. The amino-functionalized PPO obtained in this way can be crosslinked with polyfunctional acid anhydrides or epoxides (DE16 94274).

PPO which can be crosslinked is also used in the manufacture of membranes for fuel cells or semi-permeable membranes. In this area of application, the generation of bromomethyl groups by radical bromination in solution is often the first modification step. These can then be reacted, for example, with aminoalkyltrialkoxysilanes which crosslink in aqueous solution in a sol-gel process (US 455,156). The Wittig reaction can also be used to produce vinyl-modified PPO (US 4,882,057, US 4,634,742, Percec, Virgil; Auman, Brian C, Makromolekulare Chemie (1984), 185 (11), 2319-36). Another example is crosslinking by nucleophilic substitution of the bromine with NH ₄ OH, NH ₃ or ethylenediamine (EP 130 963 or US 4,468,501, De Barros, GG; Huang, MW; Frisch, HL, Journal of Applied Polymer Science ( 1992), 44 (2), 255-61). A related method is based on chloroacetylation of PPO in solution by θlθctrophile aromatic substitution and subsequent crosslinking with amines (eg EP130964). The crosslinking of sulfonated PPOs with polyamines has also been described (JP 63305904).

The reactively modified polyphenylene oxides (PPO) in the examples given could in principle also be used for a slight crosslinking, as is required for modifying the flow properties of the corresponding PPO melt. A significant disadvantage of these methods, however, is that the functionalization of PPO means an additional process step, making the process uneconomical. This applies in particular to the modification of PPO in solvents, since here the polymer is dissolved and the solvents have to be removed again after the functionalization. The direct production of reactively modified PPO by copolymerization as described above can only be carried out economically with extremely high tonnages.

JP57149317 describes the crosslinking of PPO by heating together with pentaerythritol triacrylate without the addition of initiators. A disadvantage of this method is that it is limited to the reactive but toxicologically questionable acrylates. The reactivity of methacrylates or other vinylic compounds is insufficient for the crosslinking without the addition of initiators.

The disadvantage of all the processes mentioned is the high crosslinking density. The resulting materials are infusible and therefore cannot be processed by extrusion or injection molding.

Un-modified PPO molding composition as for example as Vestoran ^® is commercially available, is not suitable for production of foams or also for blowing films suitable. The reason for this is the unfavorable flow behavior of these molding compounds. If one measures the uniaxial expansion viscosity at different expansion speeds, unmodified PPO melt shows a slight strain hardening, which is far from sufficient for a foam extrusion (Figure 1).

In addition to a direct measurement, the strain hardening can also be estimated by measuring the storage and loss modulus depending on the frequency in a melt rheological study (Figure 2). Loss and storage modulus decrease with increasing temperature, i.e. the flowability of the melt increases. However, especially at low frequencies, the loss module is significantly higher than the memory module. Deformation energy is dissipated by the melt and does not lead to an increase in tension. A rather low strain hardening is therefore to be expected for such a melt.

It was therefore an object of the present invention to provide a process with which a light crosslinking of PPO-based molding material produced on an industrial scale can be carried out economically. The method should offer the possibility of adapting the melt properties in a simple manner during the extrusion. Here, simple means that additional process steps and unusual installations on extrusion systems should be avoided as far as possible. It was therefore also an object of the present invention to modify the melt in a simple manner in such a way that the storage module is above the loss module over the entire frequency range, if possible.

The object was achieved by a process for the production of flowable, slightly crosslinked PPO-based molding compositions, characterized in that free radical initiators, vinylically unsaturated crosslinking agents and halogenating agents are added to the molding composition before processing or at a suitable point in the extruder. 09

The PPO is melted at temperatures between 220 and 350 ^° C., preferably between 240 and 300 ^° C. Suitable radical initiators should therefore have the following properties in these temperature ranges:

• rapid decay, ie half-lives at 180 ^° C. of one minute and below

• The radicals formed and the initiators should be as non-volatile as possible in the temperature ranges mentioned. Lower-boiling initiators can also be used with the help of gas-tight metering devices.

• Free radical initiators are preferred which form methyl or alkoxy radicals on decomposition, since these radicals abstract water water atoms particularly well.

It has surprisingly been found that the crosslinking of PPO-based molding compositions can be controlled by adding suitable radical initiators, preferably peroxide initiators.

It was found that radical initiators selected from the group t-butyl hydroperoxide (TBHP), cumene hydroperoxide (CUHP) and 2,5-bis- (t-butylperoxy) -2,5-dimethyl-3-hexyne (DYBP) and mixtures thereof, and mixtures with other initiators (for example tert-butyl perbenzoate) are particularly suitable.

DYBP is preferably used. With DYBP the viscosity drops slightly compared to the unmodified melt, which indicates that on the one hand there is a slight reduction in molecular weight. At the same time, the memory module becomes larger than the loss module. In contrast, TBHP leads to less degradation of the molecular weight. The viscosity increases significantly compared to the re-modified sample. 9

The results for DYBP show that this initiator is particularly suitable for modifying the melt strength. Even adding a small amount of this initiator causes the viscosity to drop somewhat, but then remains at this level with larger additions. With the result of the investigations with different amounts of DYBP to the PPO melt, the ratio of storage and loss modulus can be adjusted without the viscosity dropping too much.

The effectiveness of DYBP as a crosslinking agent can also be seen in the change in the gel content of the samples:

Table 1: Gel content and melt volume index of DYBP cross-linked samples _____

Gel content [%] MVI [ml / 10min]

_

0 35.3

0.4 11.2 0.8 12.8

1, 2 16.5

1, 5 16.5 20

It has been found that crosslinking agents have to be added to make crosslinking even more effective while avoiding even greater degradation of the molecular weight of the sample.

If initiators alone are used to influence the expansion viscosity of the melt, a drop in viscosity due to molecular weight reduction must be accepted. The additional use of crosslinking agents makes it possible to counteract the drop in viscosity. Vinylically unsaturated crosslinkers are particularly suitable. Particularly preferred crosslinkers are selected from the group diethylene glycol dimethacrylate (DEGDMA), butanediol dimethacrylate (BDDMA), hexanediol divinyl ether (HDODVA), di- [1,1,1-tris (hydroxymethyl) propane] tetraacrylate (DTMPTA), pentaerythritol triallyl ether 70 PETAE), poly (4-ethylstyrene-co-divinylbenzene) (PDVB), triallyloxy-1,3,5-triazine (TAC) and polybutadiene-1,2 (PB-1,2), especially ethylene glycol dimethacrylate (EGDMA), the Mixtures or mixtures with other crosslinkers.

It was found that the degradation of the molecular weight induced by radical initiators, with the consequence of a decrease in viscosity, can be compensated for by EGDMA as a crosslinking agent. The ratio of storage and loss module can also be influenced favorably, i.e. the memory module becomes significantly larger than the loss module (Figure 3).

The great efficiency of EGDMA as a dynamic crosslinker can be seen in the gel content. The gel content increases with the increase in the EGDMA content (Table 2). Other crosslinkers are also suitable. BDDMA is a similarly efficient crosslinker as EGDMA. Figure 4 shows the gel content and thus the effectiveness of various crosslinkers, each of which was processed in combination with 1.5 phr of DYBP.

The combination of BDDMA or EGDMA in the presence of DYBP as initiator is particularly preferred for crosslinking PPO melts. The melt volume index shows a significant impairment of the flowability of the melt when crosslinked with DYBP and EGDMA: Table 2: Gel content and melt volume index of modified PPO

_

Modification [phr] gel content [%]

PPO 0 37

1, 5 DYBP 16.5 20

0.5 DYBP 3 EGDMA 24.0 7

Less suitable crosslinkers have to be added, for example, in larger quantities. When large amounts of soluble, low molecular weight compounds are added, there is in principle the risk of plasticization.

Surprisingly, it was found that the addition of compounds which can halogenate alkyl radicals (halogenating agents) lead to a further improvement in the ratio of storage to loss modulus. The memory module exceeds the loss module several times over the entire measuring range. The flowability of the melt, measured as the melt volume index (MVI) compared to unmodified PPO, is hardly affected.

Compounds which are capable of halogenating alkyl radicals (halogenating agents), preferably from the group of N-bromosuccinimides (NBS) or 3-bromo-1-chloro-5,5-dimethylhydanione (BCDH), preferably trichloroisocyanuric acid ( TCC), their mixtures or mixtures with other halogenating agents.

By using halogenating agents, in particular TCC, the flowability of the melt can be greatly improved compared to crosslinking with EGDMA alone. The theological properties are particularly favorable for foaming or film blowing. If a halogenating agent is added to a PPO melt after modification with 1.5 phr DYBP and 3.0 phr EGDMA, for example 6.0 phr trichloroisocyanuric acid (TCC), the storage module remains significantly larger than the loss module over all frequencies (Figure 5) . The sample with TCC shows a similar rheological behavior as the halogen-free sample (Figure 3).

It was found that the melt volume index of the melt can be influenced by the use of halogenating agents compared to modification with crosslinking agents and radical initiators alone (Figure 6). Advantageously, the melt volume indices remain at a very high level, while the use of EGDMA alone leads to a considerable impairment of the flowability (Table 2). When using EGDMA as a crosslinking agent, a strong increase in the melt volume index is achieved by additionally using 4 phr or more TCC.

In the present invention, PPO molding composition is easily crosslinked by adding small amounts of additives. The additives can be added to the pelletized molding composition, for example. The crosslinking can be carried out in the same process step as the melting, for example in the plasticizing zone of an extruder. A further possibility of feeding the additive is via suitable metering devices directly into the extruder, so that the crosslinking agent and / or initiator are fed into the melt during the extrusion. The modified melt can then be further processed directly after it leaves the extruder, for example by blowing the film, or after foaming agents have been added in the extruder. The process is not limited to use in single-stage extrusion systems, but can also be used in multi-stage extrusion systems, as are often used in foam extrusion. The decisive advantage of the process is that no additional process or processing steps are necessary.

The modification attempts are carried out on a kneader. The use of a kneader is common when examining modifications to molding compounds and is used to simulate the processing conditions on the extruder. Pure PPO molding compound or PPO molding compound together with the modifiers are placed on a kneader. The mixture is kneaded for 5-20 minutes at a temperature of 220 ° C-300 ° C and a rotor speed of 20-80 min ^"1. The molding compounds are then removed from the kneader and examined.

List of pictures

illustration 1

Uniaxial extensional viscosity of time-dependent unmodified PPO melt, depending on the strain rate at 290 ⁰ C

Figure 2

Storage (G '), loss modulus (G ") and complex viscosity (eta *) of unmodified PPO melt (Vestoran ^® 1900 NF); measurement temperature 260 ⁰ C.

Figure 3

Storage (G '), loss modulus (G ") and complex viscosities (eta *) of PPO melts after modification with 1.5 phr DYBP and 4.0 phr EGDMA; measuring temperature 26O ⁰ C

Figure 4

Gel content of PPO modified with 1.5 phr DYBP and the specified crosslinkers

Figure 5

Storage (G '), loss modulus (G ") and complex viscosities (eta *) of PPO melts after modification with 1.5 phr DYBP ₁ 3.0 phr EGDMA and 6.0 phr TCC; measuring temperature 26O ⁰ C 209

13

Figure 6

Melt volume indices when modified by DYBP and TCC or by DYBP, EGDMA and TCC

The examples given below are given to better illustrate the present invention, but are not intended to limit the invention to the features disclosed herein.

Examples

The following initiators and crosslinkers are used: Table 3: Initiators in the examples

HWZ 1 min at

TBHP t-butyl hydroperoxide 85% in white oil 195 ° C

CUHP cumene hydroperoxide 88% 255 ° C

DYBP 2,5-bis (t-butylperoxy) -2,5-5-6 molar in 260 ⁰ C dimethyl-3-hexyne decane Table 4: Crosslinkers in the examples

Abbreviation Mw [g / mol]

EGDMA ethylene glycol dimethacrylate 198.22

DEGDMA diethylene glycol dimethacrylate 242.27

BDDMA butanediol dimethacrylate 226.28

HDODVA hexanediol divinyl ether 144.21

DTMPTA Di- [1,1,1-tris- (hydroxymethyl) propane] - 466.53 tetraacrylate

PETAE pentaerythritol triallyl ether 70% 256.53

Crosslink PDVB poly (4-ethylstyrene-co-divinylbenzene)

Pearls

TAC triallyloxy-1, 3,5-triazine 249.27

PB-1, 2 polybutadiene-1, 2 3000-4000

Table 5: Halogenating agents in the examples

example 1

A polyphenylene oxide (PPO) molding compound is mixed with 1.5 phr (per hundred resin, parts by weight per 100 parts by weight of molding compound) 2,5-bis- (t-butylperoxy) -2,5-dimethyl-3-hexyne (DYBP), 3 Phr ethylene glycol dimethacrylate (EGDMA) and 6 phr trichloroisocyanuric acid (TCC) added to a kneader. The mixture is kneaded for 10 minutes at a temperature of 250 ⁰ C and a rotor speed of 40 min ^"1 . Comparative example

For comparison, pure PPO molding compound is kneaded for 10 minutes at a temperature of 250 ^° C. and a rotor speed of 40 min ^“1 .

In both examples, the required torque initially rises sharply when melting. In the case of pure PPO, the torque then drops to a constant, relatively low level. With the modified melt, the torque initially even drops to values below the PPO melt, in order to reach a multiple of this value after a few minutes. Obviously, the low molecular weight additives initially act as plasticizers. After about 4 minutes of kneading time, the crosslinking effect sets in, viscosity and torque increase significantly.

Further examples are discussed in the description and were prepared in accordance with Example 1.

Claims

1. Process for the production of flowable, slightly crosslinked PPO-based molding compositions, characterized in that free radical initiators, vinylically unsaturated crosslinking agents and halogenating agents are added to the molding composition before processing or in the extruder.

2. Process for the production of flowable, slightly crosslinked PPO-based molding compositions according to claim 1, characterized in that peroxide initiators are added.

3. Process for the production of flowable, slightly crosslinked PPO-based molding compositions according to claims 1 and 2, characterized in that 2,5-bis- (t-butylperoxy) -2,5-dimethyl-3-hexyne, cumene hydroperoxide or t -Butyl hydroperoxide, their mixtures or mixtures with other initiators are added.

4. A process for the production of flowable, slightly crosslinked PPO-based molding compositions according to claims 1-3, characterized in that crosslinking agents selected from the group of ethylene glycol dimethacrylates, diethylene glycol dimethacrylates, butanediol dimethacrylates, hexanediol divinyl ether, di- [1, 1, 1 - tris (hydroxymethyl) propane] tetraacrylates, penta-erythritol triallyl ether, poly (4-ethylstyrene-co-divenylbenzenes), triallyloxy-1, 3,5-triazines or 1,2-polybutadienes, their mixtures or mixtures with other crosslinking agents be added.

5. A process for the production of flowable, slightly crosslinked PPO-based molding compositions according to claims 1-4, characterized in that halogenating agents selected from the group of N-bromosuccinimide or 3-bromo-1-chloro-5,5-dimethylhydantione, preferably trichloroisocyanuric acid, their mixtures or mixtures with other halogenating agents.

6. A process for the production of flowable, slightly crosslinked PPO-based molding compositions according to claims 1-5, characterized in that radical initiators and / or vinyl-unsaturated crosslinking agents are added via a metering device during the extrusion of the melt.

7. Use of flowable, slightly crosslinked PPO-based molding compositions according to claim 1 for the production of polymer foams.

8. Use of flowable, slightly crosslinked PPO-based molding compositions according to claim 1 for film biasing.