DE1241599B - Use of powdery high molecular weight polyethylene for the production of solid, porous bodies by sintering - Google Patents

Description

GERMAN ÄW ^ SS PATENTAMT DeutscheKl .: 39 a3-27 / 00

EDITORIAL

Number: 1241599

File number: R29574X / 39a3

j [241 599 filing date: February 1, 1961

Open date: June 1, 1967

Several proposals have already been made for the production of solid, porous bodies from polyolefins been. For example, in the German patent specification 1092 649, the production of porous moldings from polypropylene, in British patent 783 324 and in Austrian patents 205 241 and 205 242 the production of porous polyethylene bodies described. Over time it has been shown that the porous bodies made of polyethylene, manufactured according to the processes of the patents mentioned did not always have the desired strength, and that in order to achieve this strength entirely certain requirements must be met.

It has been found that excellent certainly results are obtained when using powdered, high molecular weight polyethylene with a broad melting range with a molecular weight of 250 000. 25 ⁰ C and at a molecular weight of more than 350 000 35 ° C and a molecular weight of over 500,000 is more than 45 ^° C., and with a bulk density possibly over 200 g / 1 for the production of solid, porous bodies by sintering at elevated temperature. If the starting material used for the sintering is ethylene polymers whose molecular weight and melting range are below the specified limits, the shaped bodies produced by sintering generally do not meet the quality requirements.

In-depth studies have shown that z. B. from Ziegler polyethylenes with viscometrically at 135 ⁰ C in tetrahydronaphthalene determined molecular weights of 50,000 or 100,000 and melting ranges from 126 to 134 ° C (8 ° C difference) and 127 to 142 ° C (15 ° C difference) no perfectly sintered products could be obtained at sintering temperatures of about 135 or 140 ° C. and sintering times of about 1 to 2 hours. Such products are for the most part melted or severely torn and consist of more or less large and small pieces.

If you lower the sintering temperature to about 130 ° C and shorten the sintering time to less than 1 hour, the products obtained have no strength.

Even with polyethylene feedstocks with molecular weights of about 200,000 and Sehmel ranges between about 126 and 155 ⁰ C (difference about 29 ° C) practically no perfect porous products can be produced by sintering at elevated temperature, although such sintered masses are already using pulverulent
high molecular weight polyethylene for production
solid, porous body by sintering

Applicant:

Ruhrchemie Aktiengesellschaft,
Oberhausen-Holten

Named as inventor:

Dr. Otto Liethen, Duisburg-Hamborn;

Dr. Walter Rottig, Oberhausen-Sterkrade-Nord

ao 2

are considerably better than those made from polymers with molecular weights of 50,000 or 100,000.
Flawless porous material, on the other hand, is obtained, for example, from a polyethylene with a molecular weight of about 500,000 and a melting range of about 128 to 185 ° C (difference about 57 ^D C). In such polyethylenes, the viscometrically determined molecular weight represents an average value which results from the molecular weight of the various components of which the total polymer is composed. A polyethylene with a molecular weight of about 500,000 also contains low molecular weight fractions, and its task is to combine the higher molecular weight fractions with one another during sintering. Since every polyethylene with a certain molecular weight has a certain melting point, the detection of the melting point and the broadening of the melting point to the melting range provide information about the entire molecular weight range contained in a polymer.

The observation of the melting range is a simple and valuable means of orientation about the composition of a polymer and the proportions it contains with different molecular weights. If this observation is used in connection with the molecular weight for the production of porous products from polymers of ethylene, which are prepared by one of the methods known from the literature, e.g. B. Low-pressure process according to Ziegler ₃ Natta,

709 588/338

Phillips, the result is that perfectly sintered porous molded bodies are obtained when the molecular weight of the polymer is higher than 250,000 and the melting range is at least 25 ° C. or, even better, the molecular weight is above 350,000 and the Melting range "extends over 35 ° C. · The best products are obtained when the molecular weight is above 500,000 and the melting range is more than 45 ° C. · '

To determine the melting range z. B. the microscope and the micro-melting point apparatus according to Dr. Hilbck used, the apparatus consists of a heating table "with attachment device for microscope, heated lid, thermometer with flat ground 0 to 360 ° divided into 1/1 and glass cover plate _;;., some fine olefin particles are dei sample is placed on the Heiztiscliplatte / Then covers "man'den apparatus with the glass cover plate from, the apparatus flushed with oxygen-free nitrogen and provides the heater so that the temperature per minute to about 1 up to 2 ° C. The behavior of the sample is observed with the microscope ^.

The beginning of sintering is understood to mean the first visible structural change in the polymer. At the beginning of the melting process, the outer edges of the sample become transparent, while at the end of the melting process the individual particles of the sample merge into one another and are transparent. The start of melting is about 2 to 10 ⁰ C i> higher than the Siriter tariff. The latter depends on the molecular weight distribution. The "melting range" is to be understood here as the temperature difference between the start of sintering and the end of the melting process.

It was also found that the bulk density of the polyolefin in the production of porous' material is important in accordance with the procedure according to the invention. ■ "M

• While it z. B. succeeds in producing porous plates from polyethylenes with molecular weights of about 1,000,000 and rubble - ': weights of about 200 g / 1; is the same input product for the production of z. B. filter candles less suitable. The products made from such polymers shrink more and do not achieve the same strength as the products made from input materials with bulk weights of more than about 200 g / l. It is advantageous to use polymers which have a bulk weight above about 200 g / l, in particular above about 250 g / l ^; (determined in: not processed state ". after polymerization).

Sintering with the polyethylene used in the invention is conducted at temperatures from -135 to 200 ^east C, preferably between 140 and 175 ° C carried out. The duration of the sintering depends on the type and size of the shaped body to be produced and is at least 30 minutes and can extend up to 48 hours. In most cases, a period of between 1 and 20 hours is sufficient. Inhibitors can be added to the starting material in the usual amounts of up to about 1%, as well as inorganic and organic additives or fillers, possibly also dyes.

In contrast to - Polyethylene bodies made of solid material can be produced according to the invention porous polyethylene bodies can also be colored by paints. .-

The finished products made of material with a low bulk density are lighter in liter weight and more porous than those made from polymers with higher bulk densities.

The strength of the sintered products made from polymers with low bulk densities can be reduced improve by adding polymers of the same composition with higher bulk weights. That The bulk weight can optionally also be caused by loading, e.g. B. under a press.

Differences in the bulk weights are z. B. due to different degrees of fineness of the input products. Powders with a large proportion of coarser grains have a lower bulk density than those with a larger proportion of finer grains. The degree of fineness can be adjusted during the polymerization by varying the catalyst composition, * the reaction temperature; "the flow rate DES Olefiris per · Sturide, based on grams - per amount of catalyst, -. and the stirring speed in the reactor are influenced polyolefins · increased amounts of coarse grains can be mechanically iriittels comminution machines, such _t as by means of a high-speed stirrer or in ScUa ^ 6uzmüM ^ -4dec > other- ^ igQetc ^ -Äp | i »ä> doors, process into a finer powder.» - r. ·

. .. .... . ... Example 1 ■ · ·

a) A "polyethylene" has a molecular weight of 50,000 - viscous-syrietrically determined at 135 cm ¹ tetrahydronaphthaline, a rubble weight of 225 g / l, a knock weight of 304 g / l, a sintering start of 126 ° C, a melting beginning of 129 "C and a melting end of 134 ° G • ■ Wifd M a polished, with ^: Cälciumstearät - rubbed," made of spring steel flower pot form, - which consists of a die and a patrix ', filled, the' The mold was pushed open a few times and placed for 1.75 hours in a heating cabinet at 140 ° C. During the experiment, an inert gas stream (N ₂ ) was passed through the heating apparatus. After the sintering time, the mold was removed from the drying cabinet and allowed to cool and takes the male out of the mold; the polyethylene has melted and does not adhere to the walls of the apparatus.

b) The above experiment is repeated under the conditions that the sintering temperature not 140 ° G, but 135 ° C and the sintering time is not 1.75 hours but 1 hour. Man receives a weakly sintered product that is severely torn and does not have a firm bond.

c) Another "sintering test with polyethylene is carried out in the apparatus given in Example 1, a) carried out. The constants of the input product k

<■ are: molecular weight 100,000, bulk density 259 g / 1, tap weight 345 g / 1, initial value 127 ^; C, start of melting 129 ° C, end of melting 142 ° C. The sintering temperature is 140 ° C and the sintering time is 1.5 hours. The polyethylene is sintered and severely torn.

d) A polyethylene with the following constants: molecular weight 500,000, bulk density 246 g / 1, Knock weight 334 g / 1, sinter tariff 128 ° C, start of melting 142 ° C, end of melting 185 ° C, is in the mold of Example 1, a) filled and sintered at 140 ° C. for 2 hours. The sintered product has good strength and is not torn.

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Example 2; Example 8 ■ - ---- w! ■■ Tu '· hi •• ^ v-' Vr t · JI *. ·· - W A polyethylene is processed with the following constants; Constants- · "· ^; molecular weight 1000,000, bulk density 225 g / 1, ^« ·,

Tap weight 355 g / l, start of sintering 133 ° C, melting 5 molecular weight 1Ö00,000

beginning 143 ° C, melting end, 200 ° €, in the form of the bulk density ....... _r ........ 172 g / 1

Example 1 a) and sintÄ 2! Hours at 145 ⁰ C. The knock weight 250 g / 1

Product is flawless ^! dirchsinterert andvjjesitz. νr120 ° C. ·; ..-.- .... .χ -, .........>, .- 269 / kg / cm ²

good strength. j (tear strength)

'· J. 'o- / jl20 ^J C 34 kg / cm ² ,

'With -SDielS ":." ··· · ·. ■, '·. (Tensile strenght)

"- -v ^P i>;;. · .- '5 k 120 ° C _: ,: 913 7o ■.

If you fill in the fornixes example I, a) a poly-: - - - (elongation at break)

ethylene having: a molecular weight of 1,000,000; . -ZST value. , ..; -. . 3.3 kg / cm ² j

a bulk weight of 17έ g / 1, a knocking weight of 15: ....:. ... '. . ' : · - '

of 250 g / 1, a sintering start of 137 ° C, a [The ZST value is a measure of the melt-melting start of 142 ° C, a melting end of., -Viscosity and the flow behavior of the plastics.

215 ° C, and it provides at 145 ^C .C 2 hours in a term is understood the normal stress, based

drying cabinet under nitrogen, so receives on the sample cross-section, which is necessary in order to

is a sintered product that is shrunk 20 a dumbbell sample (land length 18 mm, Stegbreitei;

and a " ^r lower strength compared to the 4mm) m glycerine at 150 ° C in 10 minutes by" 600 ° / ₀ ^:

Example 2 has i ζμ stretch.] "';'

I I. I The polyethylene is in a Winkekähmen example 4, (^ ⁵⁰ ■ ³⁰⁰ mm), the bottom one with Siliconol. and i> ..-, ·]> --35 calcium stearate rubbed in, 2 mm thick, from 1 part by volume of the product from example 3 made of stainless steel. The dump height; is with I volume part of the # insert product from at- 10 mm. You place one mixed with Siliconpl and Calciumspiel 2 ^. This, j-Miscriung fills in the ijnan stearate rubbed 2 mm thick StahlplattQ aJls'iösfei form of Example 1, a), and j they sinters 2 hours free material onto the powder. Of the; filled angles at 145 ° C. The sintered product obtained is 30 rähmen is shrunk for 2 hours in a 150 ⁰ Cerwarmteri less, and has higher strength ICreate a drying oven, through which a weak StickstQffgegenüber j deni experiment 3. C ":. ~ .S ·"'actual current is passed, good. '"After' ^: <the sintering time j j j I take the frame out of the ί drying cabinet; ... B eisjpi ei : 5rcc \ 'and; let it cool down. The solid porous evenly

ι ^! j: _ ...; . ^ 5._ fully sintered polyethylene pulp has a specific

Polyethylene of low molecular weight. of weight of 0.298 g. . .

1000 OOO ¹ ₃ a bulk weight of 172 g / 1, one -. . . " ^: ."

Tapping weight of 250 g / 1 is 15 minutes with example y

50 kg / cm ² loaded, the gepreßte.Produkt in the high. . - The trial 8 is made with a polyethylene that is a

revolving stirrer for 30 seconds at 9000 rpm and 40. has a higher bulk density. but the others

beat and then sifted (144 stitches per. constants are practically the same, repeated.

Square centimeters) The sieved product has a; -. _ _Mo i _eku i _arweight ......... l 000 000 - '

Schuttgejicht of 202 | / ^ nd em knocking weight of _bulk weight 255 g / 1 '

270 g / 1. It Wd _t Filled into the form of Example 1, a) .. Tap weight., L L 352 g / 1

and 2 hours; sintered at 145 C. , ". · 45 _{ffR 120} ° C ^!. 254 kg / cm ²

The sintered product has a greater strength than 20 ° C 34 kg / cm ²

than that of experiment 3. SrIIO ⁰ C '888%

- ·. · ^; '-. ·· "'''ZST value 3.35kg / cm ²

Example 6. · - · '' '- · ■ ■■

50 The sintering time is 2 hours and the sintering test of Example 2 is repeated with the sub-temperature 150 ° C. The solid porous and equal difference that one repeats below 450 ecm. Polyethylene moderately sintered mass, has a specific weight of 0.367 g before being filled into the mold 2 g of a blue color. stirred evenly. The sintered product has;. - the same strength as that of experiment 2. 55 eisp iellO

The starting product from experiment 1, d) is extracted for 8 hours in example 7 with tsooctane. The. Amount of extract

....;. · ,:. . , ·. . is 1.1 percent by weight. The extracted dry

50 ecm polyethylene from 1 example 2 are combined with 60 polyethylene has the following melting range:

0.5 g of N-phenyl-N'-cyclo-hexyl-p-phenylenediamine, sintering start at 133 ° C

30 seconds at a rpm of 6000 in a high-speed melting start at 141 ° C

Stirrer struck. This mixture will evenly melt at 214 ° C

stirred under 400 ecm of the colorless polyethylene.

The powder mixture is filled in the form of examples 65 If this extracted product in the flower pot Game 1, a) and is sintered for 2 hours at 145 ° C. The form of Example 1, a) filled and 2 hours in the case of product is well sintered and has a good 140 ° C sintered, so you get a porous mass, strength. which does not have the strength of example 1, d).

Claims (1)

However, if the extracted and dried product is ^{sintered for 2 hours at 145 °} C. in the flower pot shape of example 1, a), the porous product has the strength of test 2. Example 11 Three different polyethylenes with a molecular weight of 1 · IO ⁸ _5, whose melting range was between about 140 and 210 ° C., but whose bulk weights differ considerably, were sintered on the one hand at approximately normal pressure and on the other hand at elevated pressures. The values obtained for the air permeability at various admission pressures can be found in the tables below. Table I. The sieve analyzes of the products used in a test sieve machine showed a sieving time of 10 minutes the following results: 17.85 26.15 35.4 I-IO ⁶ I-IO ⁶ I-IO ⁶ Bulk density, g / 1 172 255 339 Mesh size, mm Weight percent below 0.06 1.21 1.25 3.14 0.06 to 0.12 21.15 63.61 36.80 0.12 to 0.25 42.60 31.60 46.10 0.25 to 0.5 28.40 3.54 12.10 0.5 to 1.0 6.64 0.0 1.86 Table II Molecular weight 1 IO ⁸ 1-10 « 1-10 « Melting range _f ⁰ C 147 to 213 143 to 200 138 to 210 Bulk density, g / 1 172 255 339 Reaction tempera tur, ⁰ C 156 156 156 Lower heating plate, ⁰ C 125 125 130 Upper heating plate, ⁰ C 145 145 150 kg / cm ^a (atü). 1.8 ») 0.002 *) 1.8 o) 0.002 *) 1.8 ·) 0.002 *) Breathable speed, l / h / cm '.. measured at 20th 50 100 7.5 20th 20th 50 7.5 20th 20th 50 74 20th Apparent speci fish weight .. g / cm ³ g / cm ³ g / cm ^s Sintering time 5 minutes 6.5 16.1 30.7 0.515 15 minutes 6.5 16.2 31.0 0.509 20 minutes 10.5 25.2 0.534 17.6 36.0 0.628 30 minutes 5.7 14.4 27.5 0.532 11.5 26.7 0.529 17.3 35.1 0.622 45 minutes 14.0 31.0 0.515 16.8 34.5 0.640 60 minutes 3.4 7.7 15.0 +0.600 11.3 26.4 0.519 12.5 29.0 +0.664 90 minutes 10.0 23.2 0.553 9.5 22.6 +0.682 105 minutes 26.1 44.3 0.305 21.8 40.0 0.57 120 minutes 18.8 35.9 0.429 +3 = glossy underside. *) When the pressure was increased to 0.1 atm there was only a slight decrease in air permeability. °) When the pressure was increased to 2.5 atmospheres, the air permeability decreased further. Claim: Use of high molecular weight polyethylene in powder form with a wide melting range, the one with a molecular weight of 250,000 at least 25 ° C and with a molecular weight of more than 350,000 35 ° C and with a molecular weight of over 500,000 more than 45 ° C and with a possibly over 200 g / 1 lying bulk weight for the production of solid, porous body by sintering at elevated temperature. Considered publications: German Patent No. 1092 649; Austrian Patent Specification No. 205 241,205 242; British Patent No. 783 324. 709 588/338 5.67 0 Bundesdruckerei Berlin