CH646960A5 - CYANURIC ACID MELAMINE REACTION PRODUCT AND THESE MOLDS CONTAINING THIS POLYAMIDE AS A FLAME-RETARDANT ADDITIVE. - Google Patents

Description

The present invention relates to a flame-retardant active substance produced from cyanuric acid and melamine and to molding compositions containing polyamide containing this active substance.

Molding compositions containing polyamide are generally flame-retardant modified by adding halogen-substituted aromatics, together with finely divided antimony trioxide. The main disadvantage of this formulation is the formation of hydrohalic acids during combustion, which in itself is problematic in particular in times of increasingly strict requirements for environmental protection. In addition, such hydrohalic acids have an extremely corrosive effect on metal parts such as electrical switching elements and electronic components.

Therefore, other products with flame retardant properties that do not have these disadvantages were searched intensively. According to DE-OS 2 453 621 cyanuric acid and its lower alkyl esters, partly in combination with formamide, have been proposed as a flame retardant system for polyamides. The description deals in particular with the lack of temperature resistance and the difficult processing conditions. Cyanuric acid can therefore only be used for copolyamides, low-melting special polyamides or very low-viscosity polyamide 6 types.

DE-OS 1 694 254 describes melamine as a flame retardant and substitution products of melamine. These flame retardants only have a minor influence on the mechanical properties of the polyamide molding compound added. The temperature resistance of the melamine is good, so that not only polyamide 6, but even polyamide 66 to be processed at high temperatures can be set to self-extinguishing. Even when glass fibers are present, they become self-extinguishing

Properties of the polyamide molding compound improved.

Not mentioned in the above DE-OS is the high sublimation rate of the melamine at temperatures above 250 ° C, which leads to deposits in the processing tool and thus to production problems, and the almost unlimited solubility of the melamine in warm water. Due to the high water absorption of polyamide 6 and polyamide 66 for plastic, the flame retardant melamine is washed out if the molded parts are in contact with water for a longer period of time, which means that the flame retardant effect is lost. Because of the high tendency of melamine to sublimate, efflorescence occurs on the surfaces of the molded parts, which affects the electrical properties.

DE-OS 2 740 092 now mentions a flame protection system which does not have any of the above disadvantages. The defined addition compound of melamine with cyanuric acid, which is prepared by reacting cyanuric acid with melamine in a molar ratio of 1: 1, is described as the flame retardant active ingredient. This flame retardant is also sparingly soluble in warm water. For example prepared by mixing an aqueous solution of cyanuric acid with an aqueous solution of melamine and reacting the same at about 90-100 ° C. with stirring, the precipitate formed being filtered off. Unfortunately, the temperature resistance mediated by this melamine cyanurate is not sufficient for polyamides such as polyamide 66 to be processed at high temperatures. So in said DE-OS 2 740 092 on page 13, lines 6-9: "It is preferable to heat the mass in the molding step to a temperature below 270 ° C and especially below 250 ° C in order to decompose the To prevent flame retardants ». It has therefore been shown in practice that pure polyamide 66 cannot be modified with melamine cyanurate as a flame retardant. In order to be able to take advantage of the advantages of the melamine cyanurate to a certain extent with polyamide 66, low-melting copolyamides of polyamide 66 with polyamide 6 were used. However, these have a significantly reduced heat resistance and a reduced stiffness and therefore no longer the specially preferred properties of polyamide 66.

Because of its excellent properties, however, polyamide 66 from the class of polyamides is the most popular construction material with the largest market share. Its advantages are: high heat resistance, which mainly has a positive effect on mineral-filled or glass fiber-reinforced types, very fast processing cycle and excellent mechanical and electrical values. There is therefore a great need for a polyamide 66 which is also suitable for electrical and electronic use and is therefore halogen-free modified and has good self-extinguishing properties.

DE-AS 1 173 641 now describes the use of elementary, red phosphorus for the flame-retardant treatment of thermoplastics, including polyamide. The incorporation of red phosphorus, also in polyamide 66, proved to be possible in principle and self-extinguishing properties could thus be achieved. However, due to the extraordinary reactivity of the elemental phosphorus during its production and incorporation into the polymer, special precautionary measures must be taken. There is therefore an extensive literature dealing with phlegmatization, i.e. Reduction in the reactivity of the red phosphorus, e.g. US Pat. No. 3,951,908, which describes an encapsulation of the red phosphorus in caprolactam, or in the data sheet for phosphorus products EXOLIT 505 from Farbwerke Hoechst, Knapsack factory /

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646960

FRG, dated: 05/76, which describes the processing of such a caprolactam-capped red phosphor with polyamide 66 for the production of flame-retardant compositions. From this it can be seen that work must be carried out under inert gas and special ventilation devices are required in the work rooms so that the poisonous phosphines that may be formed can be effectively extracted. In addition, the resulting products are colored intensely brown, which is why - apart from black coloring with soot of high opacity - practically no other coloring is possible.

Surprisingly, flame-retardant molding compositions having thermoplastically processable polyamide have now been found, which do not have the above disadvantages. The molding compositions comprising polyamide according to the invention are characterized in that they contain a thermoplastically processable polyamide or polyamide mixture or a blend of polyamide and another thermoplastic, and the reaction product of 1 mol of cyanuric acid and at least 2 mol of melamine. Advantageously, the thermoplastic component consists entirely of polyamide, with 3-30 parts by weight of the reaction product according to the invention preferably being used for 97-70 parts by weight of polyamide. The flame-retardant reaction product should advantageously be present in the molding compositions in the finest possible form.

All types of thermoplastically processable polyamides are suitable as polyamides. It is of course particularly advantageous to use the high-melting polyamide types and high-viscosity polyamide types which, because of their high melt viscosity, require a high processing temperature. Examples here are polyamide 66, the polyamide made from isophthalic acid and hexamethylene diamine, transparent polyamides according to US Pat. No. 4,232,145 (or

DE-OS 2 642 244) and generally all transparent polyamides with glass transition temperatures which are above 150 ° C, also polyamide blends, e.g. of polyamide 66 with other polyamides, especially with transparent polyamides with a glass transition point above 150 ° C, or of amorphous polyamides with a glass transition point above 150 ° C with any kind of other polyamides. Furthermore, so-called polymer alloys, i.e. intimate mixtures of two or more polymers with which the compound according to the invention is made flame-resistant, at least one component of the alloy having to be a polyamide. Such alloys or «polymer blends» exist e.g. made of: polyamide and a polyester, e.g. Polyamide 66 and polybutylene terephthalate or poly-ethylene terephthalate. Another example is polyamide 66 with polyethylene terephthalate as well as with an olefinic copolymer, e.g. Polyethylene and acrylic acid. The acrylic acid can be partially neutralized and can contain metal ions such as Na, Zn, Ca, Mg, Pb etc. instead of the acidic proton. Such olefinic polymers are known under the name “ionomers”. Further examples are polymer alloys made of polyamide 6, 66 or 12 with a transparent polyamide, e.g. according to US Pat. No. 4,232,145, and an ionomer resin or polyamide 12 with polyethylene terephthalate and an ionomer resin. If olefinic polymers or copolymers are also used as alloy components, these should be as free as possible of double bonds.

The polyamides, polyamide alloys or the polymer alloys can contain the usual processing aids, stabilizers and fillers and reinforcing materials, pigments and dyes.

That the combination of 1 mol of cyanuric acid and 2 mol of melamine (so-called «dimelamine cyanurate») has such a high processing stability that it allows polyamide 66

And here, too, the excellent processing of the highly viscous types and making them flame-resistant is surprising. Even with a suitable choice of concentration, the flame retardant does not lose its effectiveness when exposed to warm water. Furthermore, the mechanical and electrical properties of the thermoplastic compositions are influenced only insignificantly. The processability and especially the injection cycle of the polyamides modified with this compound are excellent. In addition, coloring in many colors is easily possible because the flame retardant has only a slightly opaque color.

The active ingredient dimelamine cyanurate according to the invention has extremely interesting properties. It is advantageously produced by the process described in more detail below during incorporation into the polyamide,

by incorporating 3-30 parts by weight of an intimate mixture of melamine cyanurate 1: 1 with at least 1 mol of melamine directly into 97-70 parts by weight of the polyamide melt, in particular in polyamide 66.

Here, the melamine cyanurate 1: 1 is first prepared and finely pulverized in accordance with the aforementioned DE-OS 2 740 092. The melamine cyanurate 1: 1 is then mixed with finely ground melamine, e.g. homogeneously mixed in an intensive mixer, such as a Henschel mixer. This mixture is then mixed with intensive kneading e.g. incorporated into the polyamide melt in a double-shaft kneader, for example a ZSK 30 from Werner & Pfleiderer, Stuttgart / FRG. For a polyamide with a low melt viscosity, this can be done without further additives. If a medium or highly viscous polyamide is used, it is advisable to add a plasticizer, for example a so-called metal soap (calcium stearate or magnesium stearate). Other effective processing aids are amides such as e.g. the amide from tridecylamine and lauric acid, bisamides such as ethylene bisstearamide, also bisureides or simple amines with long-chain alkyl radicals, which can be linear or branched and e.g. Contain 12-30 carbon atoms. A selection of suitable plasticizers or processing aids is e.g. listed in the mentioned DE-OS 2 740 092.

The melamine cyanurate 1: 1 is incorporated into the polyamide in a preferably finely divided form. The molding composition according to the invention has advantageous flame-retardant properties. Advantages are the better temperature stability, so that even medium and high-viscosity polyamide 6 can be processed without problems, and above all the poor solubility of this compound in warm water. There are hardly any sublimation effects during processing and efflorescence can only be observed to a small extent in the state of high temperature and humidity. As a result, the electrical properties remain largely unaffected.

The molding compositions according to the invention can be processed into moldings of any kind. If such a shaped body is conditioned in warm water or remains in contact with warm water for a long time, the second bond of the cyanuric acid with the melamine is dissolved in the dimelamine cyanurate and one mole of melamine is released. One can imagine this in such a way that instead of the melamine, water is attached via a hydrogen bond and the cyanuric acid and displaces the melamine. This is consistent with the fact that cyanuric acid crystallizes out of water in the form of the dihydrate. The released melamine can now be extracted with warm water. However, the remaining 1: 1 compound, the melamine cyanurate 1: 1, is stable to water splitting, is poorly soluble and thus remains as an effective flame retardant in the polyamide matrix.

E.g. Polyamide 66 with 10% by weight of the

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If the compound is modified to be flame-resistant and the product is subsequently exposed to warm water, the flame-retardant effect is retained by the melamine cyanurate oil: l remaining in the matrix.

The following examples illustrate the invention. The abbreviations that appear mean the following:

Mei - melamine

MC - Melamine cyanurate (1: 1)

PA - polyamide

PBTP - polybutylene terephthalate.

Further abbreviations appearing in the tables are explained there.

Examples

General procedure

In the following examples and comparative examples, the flame retardants Mei or MC or MC and Mei were incorporated into various polyamides or polyamide blends or polymer alloys.

When incorporating the flame retardant according to the invention, MC and Mei were previously in the most finely divided form possible on an intensive mixer, e.g. Henschel laboratory mixer, intensively premixed.

In order to achieve an optimal distribution of the flame retardant during incorporation, a plasticizer was usually used.

A twin-shaft kneader from Werner & Pfleiderer, Stuttgart / FRG, type ZSK 28 was used to incorporate the additives.

In preparation for the incorporation of the flame retardant, the granules made of polyamide (or granulate mixture if a polyamide alloy or a polyamide blend was used) were first powdered with the lubricant and then mixed intensively with the flame retardant. This mixture was then fed to the twin-shaft kneader via an inlet funnel. The pair of screws was kept at a speed of approx. 150 revolutions per minute, the melt in the extruder having a mass temperature of approx. 280 ° C. The

The melt was drawn off as a strand over a water bath and the strand was then granulated. The resulting chips were dried to a water content of about 0.05% by weight and then sprayed on a piston injection molding machine to give flat bars 12 cm long and 1.3 cm wide. The thickness of the bars was 0.8, 1.6 or 3.2 mm (corresponding to Vn, Vu or Ys inches). Their burning behavior was then determined using the UL 94 method (standard from Underwriters Laboratories Inc., io Melville, USA).

Examples 1-10

(Table 1)

The procedure was as described under “General Procedure” and MC or mixtures of MC with Mei in PA 66 or other polyamides or an alloy of PA with PBTP were incorporated.

The results are summarized in Table 1. They show that with MC or mixtures of Mei and MC, which are 20 below the stoichiometric ratio of 1 mol Mei per MC, it is not possible to produce a perfectly processable PA 66 material. If the ratio of 1 is reached (or slightly exceeded for practical reasons), perfect parts can be injected from PA 66, 25 whose flame-retardant properties depend on the amount of the flame retardant system used, but for example at 10% by weight flame retardant (example 5) achieve UL 94 classification VO even on 0.8 mm thick rods.

30 Examples 6-10 correspond to other polyamides or blends which can only be processed properly at high mass temperatures and which could all be sprayed to give perfect test specimens with good, self-extinguishing properties.

35 In Tables 1 and 2 below:

*) - Comparative example

CaS - calcium stearate

A - aliphatic primary amine (molecular weight 267)

40 FT - extinguished

VO - self-extinguishing, best flame protection class

NK - not classifiable, i.e. bad effect

Table 1

For polymer anti-flame agent processing UL-94 classification comments play in% by weight of test specimen thickness, mm

Type Specification Mei MC Mei: MC Art.% 0.8 1.6 3.2

1 * PA-66

2 * PA-66

medium viscosity injection molding type medium viscosity 0.5 injection molding type

3 * PA-66 medium viscosity 2.0

Injection molding type

4 PA-66 medium viscosity 3.0

Injection molding type

5 PA-66 medium viscosity 4.0

Injection molding type

6 Amorphous. CoPA highly viscous for 4.0 acc. Injection molding type

US 4232145 and Extrusion Ex. 23

10 CaS 0.2

8 1: 7.9 A 0.5

8 1: 1.97 A 1.0

5 1.22: 1 A 1.0 VZ VO VO

6 1.35: 1 CaS 0.3 VO VO VO

7 1.16: 1 CaS 0.3 VZ VO VO

Foaming and strong surface defects during processing

Surface defects

Surface defects

Flawless surface up to mass temp. 300 ° C

Flawless surface up to mass temp. 300 ° C

Flawless surface up to mass temp. 300 ° C

646960

Table 1 (continued)

Example polymer play

Type

Anti-flame agent processing UL-94 classification Remarks in% by weight of test specimen thickness, mm

specification

Mei MC Mei: MC Art wt% 0.8 1.6 3.2

7 PA from Isophthal. + Highly viscous di-aminohexane 4.0 6.0 1.35: 1 CaS 0.3

CoPAaus85% high viscosity 4.0 7.0 1.16: 1 CaS 0.3 caprolactam + extrusion type 15% Laurolact.

9 Pa-66.80% PBTB 20%

10 amorphous. PA acc.

Ex. 6 + PA 66 acc. Ex. 2,

1: 1

as Ex. 1 4.0 7.0 1.16: 1 CaS 0.3 mean.

Injection molding type

VO VO

VO VO

VZ VO

4.0 7.0 1.16: 1 CaS 0.3 VZ VO VO

Flawless surface up to mass temp. 300 ° C

Flawless surface up to mass temp. 300 ° C

Flawless surface up to mass temp. 300 ° C

Flawless surface up to mass temp. 300 ° C

Comparative Example 11 and Comparative Example 12 (Table 2)

12% Mei was incorporated into a PA 66 according to Example 1-5 and flat bars 1.6 mm thick were produced therefrom for the burning test. The material shows self-extinguishing properties according to UL 94, VO, at 1.6 mm. These rods were then immersed together with rods from example 5 for 4 hours in boiling water and then subjected to the UL 94 firing test. The results are summarized in the following table:

Table 2

Example No.

PA type

Flame retardant

UL classification,

medium

1.6 mm flat bar

Mei MC

11 VergL-

1 PA 66

12 -

NK

example

{• corresponding

12 Example

J Ex. 1-5

4 6

VO

25 Table 2 shows that Mei is a water-extractable flame retardant, while with the system according to the invention the flame retardant effect is retained even after prolonged contact with boiling water.

30 Example 13

Solids were produced from self-extinguishing PA 66 in accordance with Example 5, and the mechanical properties compared to the same PA 66 base type, but without flame retardant, were determined 35 (see Table 3).

It was found that the polyamide 66 according to the invention, according to Example 13, does not differ significantly from the unmodified PA 66. It showed almost identical strength values in accordance with the DIN 53455 standard, has the advantage of increased stiffness (DIN 53457 and DIN 53452) and hardness (DIN 53456), but on the other hand drops somewhat in toughness (DIN 53453), it is important that the good value oB = is achieved without breakage in the condition that is important for practical use in terms of impact strength. 45 Furthermore, the burning test according to ASTM D 2863 was carried out on the PA 66 according to the invention and a value for% O2 of 33 (LOI value) was found.

Table 3

property

standard

unit

Mechanical specifications

Invention. PA 66 corresponds to Example 5

pure, medium-viscosity PA 66 base type dry.

condition

dry

condition

Flow resistance

DIN 53455

N / mm2

90

45

85

55

Elongation at flow

DIN 53455

%

<5

<5

<5

25th

Breaking strength

DIN 53455

N / mm2

85

50

85

45

Elongation at break

DIN 53455

%

5

25th

15

175

Tensile modulus

DIN 53457

N / mm2

3000

1700

3600

1600

Bending stress

DIN 53452

N / mm2

130

55

120

50

Bending modulus of elasticity

DIN 53452

N / mm2

3000

1300

2500

950

Ball indentation hardness 30 "

DIN 53456

N / mm2

130

65

95

50

Shore hardness D

-

-

83

75

85

75

Impact resistance 23 °

DIN 53453

kJ / mm2

50

if

if

if

Notched impact strength 23 °

DIN 53453

kJ / mm2

2nd

5

4.5

12

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Example 14

(= PA used according to example 5) and comparative example 15

In this example, the processability of PA 66 with flame retardant according to Example 5 was compared to PA 66 containing 10% MC as an anti-flame additive. For this purpose, plates with an edge length of 10 cm and a thickness of 3 mm were injected at temperatures of the polyamide melt of 270-300 ° C and these were compared in terms of surface quality.

The results are summarized in Table 4. They show that with the flame retardant according to the invention, plates with a perfect surface could be obtained up to a mass temperature of 30 ° C. (the highest temperature tested and normally used for the processing of PA 66), while it was modified when the same PA was modified 66-type with MC failed to produce flawless plates.

Table 4

example

Mass T emperature

Assessment of the test specimens

the PA melt ° C

14

275

Very well

280

Very well

290

Very well

300

Very well

15

275

slight surface defects

(Comparative

280

clear surface defects

Example)

290

severe surface defects

300

very strong

Signs of decomposition

Examples 16-19 In the following examples or comparative examples according to Table 5 was incorporated into PA 66 (medium-viscosity injection-molding type) 30% mineral and the flame retardant system according to the invention in a concentration of 15% by weight, 9% by weight MC and 6% by weight Mei being used. At a mass temperature of 280-290 ° C, rods were produced in accordance with Examples 1-10 and the self-extinguishing properties were determined according to UL94.

The classification VO was measured on the rods, which all had a perfect surface, up to a layer thickness of 1.6 mm. At the same time, 35 small DIN beams were injected from it and the bending and impact values were determined according to DIN 53453.

As Table 5 shows, these self-extinguishing formulations based on PA 66 are significantly stiffer than PA 66, which is only equipped with flame retardants.

Table 5

Example No.

(* = Compare example)

mineral

Mechanical specifications

Impact resistance DIN 53453

Bending stress DIN 53452 dry

Bending modulus of elasticity DIN 53452 dry

Ball indentation hardness

DIN 53456 dry

16

Alum. Silicate, ground to an average 0 of 1.2 u, kaolin type d. Engelhard, Edison, N.J./USA

20th

205

4700

190

17 * without anti-flame agents as above

40

197

4500

185

18th

Calcium meta-silicate on medium. Grain size of 10 (i from Interpan, Willsboro / USA

16

220

4900

190

19 * without anti-flame agent

21st

205

4600

187

B

Claims (7)

646960 1. reaction product of cyanuric acid and at least 2 moles of melamine or melamine cyanurate 1: 1 with at least one mole of melamine as a flame-retardant active ingredient. 2. Flame-resistant, polyamide molding compound, characterized in that it contains thermoplastically processable polyamide or polyamide mixture or a blend of polyamide and another thermoplastic and the reaction product according to claim 1. 2nd PATENT CLAIMS 3. Molding composition according to claim 2, characterized in that the thermoplastically processable polyamide is one whose processing temperature is above 270 ° C. 4. Molding composition according to claim 3, characterized in that it contains polyamide 66 as a thermoplastically processable polyamide. 5. Molding composition according to claims 2 and 3, characterized in that the thermoplastically processable polyamide is an amorphous polyamide made from isophthalic acid and diaminohexane. 6. Molding composition according to one of claims 2-5, characterized in that it contains, based on polyamide, 3-30 percent by weight of the reaction product according to claim 1. 7. A process for producing a molding composition according to any one of claims 2-6, characterized in that 3-30 parts by weight of an intimate mixture of Melamincya-nurat-l: l with at least one mole of melamine directly in 97-70 parts by weight of a thermoplastically processable polyamide having melt incorporated.