SE462044B - PROCEDURE FOR REINFORCEMENT OF GUM WITH GUM AMPOLYMERIZING CELLULOSA FIBERS AND FIBER ARMED GUM PREPARED THEREOF - Google Patents

Description

462,044 The present process for fiber reinforcement of rubber is claimed in claims 1-4 and a cellulose fiber reinforced rubber is defined in claims 5-10.

Both natural rubber and synthetic rubbers can be reinforced according to the method of the invention. The synthetic rubbers are preferably non-polar, such as styrene butadiene rubber (SER), butadiene rubber (BR), isoprene rubber (IR), ethylene propenediene rubber (EPDM), ethylene propylene rubber (EPM) or norbornene rubber (PNR). chloroprene rubber (CR), acrylic rubber (ACM) or nitrile rubber (NBR) may also be considered. Particularly reinforced natural rubber, styrene-butadiene rubber and nitrile rubber are of interest in this case.

Cellulose fibers of different origins with suitable aspect ratio, ie which give the selected rubber optimal reinforcement with regard to use, are modified by graft copolymerization with at least one monomer of alkyl or alkenyl acrylate or methacrylate or a copolymer between two or more of these monomers. Suitable monomers are C; - Ci; alkyl acrylate. O; - 01, alkenyl acrylate, C 1 -C 12 alkyl methacrylate or C; - Gi; alkenyl methacrylate, monomers containing alkyl or alkenyl groups having 1 to 8 carbon atoms are particularly suitable. Cellulose fibers grafted with butyl acrylate have been found to be particularly suitable for fiber reinforcement of rubber, but all the grafted cellulose fibers show an increased adhesion and give a rubber with improved strength and low elongation.

The graft copolymerization of the cellulose fibers can take place by various grafting methods and the invention is not limited to the grafting process exemplified below. In particular, the amounts of monomer and cellulose fibers must be tested with respect to the reactor used and the desired modification. The inoculation can also be initiated with other methods, such as radiation.

E¿emg§1_1 Grafting of cellulose fibers Various monomer mixtures were used to produce grafted cellulose fibers. The monomer mixtures in the three cases exemplified below consisted of: 462,044 I) so m 1ylyl acrylate (sn) II) 25 ml butyl acrylate And 30 ml allyl acrylate (ABA) III) 25 ml butyl acrylate and 25 ml crotyl acrylate (CBR).

For use in the grafting reaction described below, an initiator solution was prepared from three solutions: Solution A: 14.46 g Na.P = Ov x 10 H 2 O dissolved in distilled water to a volume of 250 ml. PH value of the solution Adjusted to 6 by adding conc. sulfuric acid. At this pH, the pyrophosphate in the form of H = P = O12 ions Solution B: 6.41 g MnSO1 dissolved in dist. water to a volume of 100 ml.

Solution 0: 1.26 g KMnO1 dissolved in dest. water to a volume of 100 ml.

For a reaction volume of 10 l, 150 ml of solution A was used to give an H = P = Ov2 concentration of 2 mM in the final solution and 25 ml of each of solutions B and C to give an Mn ° * concentration of 1 mM in the final solution. Solutions A and B were mixed before the addition of C to avoid precipitation of MnO =.

In a 10 l glass flange flask equipped with stirrer, thermometer, dropping funnel, gas inlet pipe, cooler and a thermostated jacket, 200 g of dry cellulose of the Stora Fluff®> brand (bleached sulphate pulp based on pine, manufactured by Stora AB, Sweden) was charged and defibrated by MoDo Converting Machinery AB, Sweden). The reactor was closed and vented by alternating evacuation and nitrogen purge. Distilled water acidified with 11 ml conc. sulfuric acid and containing one of the above-mentioned monomer mixtures was added to a total reaction volume of 10 l.

Water and monomer had been deaerated before the addition to the reactor in the same way as the cellulose. Stirring, heating and nitrogen bubbling of the reactor are started and when the mixture has reached 30 ° C, the deaerated initiator solution, prepared as above, was added.

After three hours, the reaction was stopped and the reactor contents were transferred to a filter funnel and washed with distilled 462,044 water and methanol. The product was dried to constant weight in vacuo at room temperature.

The results of the grafting reaction are shown in Table 1 and show that the monomer butyl acrylate gives the highest yield of polymer on the modified cellulose fibers.

Table 1: EQLÄDQI1H9_QI_QQ1lHlQââilDšL_E§nQm_! ME fl inS Inoculum "Add on" * Dubbelbindningar X pmol dubbelbindn./gi X ympade, Xm2âQ_ilQ§Lr ,, mšïêf butyl acrylate 16,2 7 acryl-acrylate 17,2 7 acryl-acrylate *) "Ådd On" = S_IEEíQ_2QlIE§LX 100 g of grafted product The amount of double bonds remaining was determined by bromination with pyridine hydrogen bromide perbromide at room temperature in a 75:25 volume percent mixture of methanol and carbon tetrachloride (see Tunncliffe S, J. Appl. 14, pp. 827 (1970)).

The treated cellulose fibers are mixed into conventional rubber compounds in an amount of from 5 to 70 Phr (parts per hundred rubber), preferably 10 to 40 Phr. The rubber mixtures contain conventional chemicals necessary for vulcanization, such as an activator and other necessary additives and fillers, as well as a processing oil and an antioxidant. The rubber compounds are mixed with the grafted cellulose fibers and vulcanized as further described in Example 2 below.

O! 462 044 E¿gmp§1_2 Manufacture of fibrous rubber.

Rubber mixtures consisting of the following ingredients were prepared: - Month Phr Natural rubber (SMR CV50) 100 Dutrex 729 (processing oil) 4 Stearic acid 2 ZnO 5 Carbon black (N 330) 20 TMQ (see below) 2 NOTE (see below) 0.5 Sulfur 2 .5 Cellulose fibers grafted acc. Example 1 or 10, 20, 30 or 40 Note: Stearic acid, ZnO, CBS and sulfur are vulcanizing chemicals, with CBS (cyclohexylbenzotriazylsulfenamide) being an activator. TMQ (polymer trimethyldihydroquinoline) is an antioxidant.

The various rubber compounds were processed in a rolling mill and rolled into 2 mm thick test plates. The plates were vulcanized at 160 ° C to take, ie the time for 90 X of maximum torque was reached, calculated from the rheometer curves obtained using a “Monsanto Oscillating Disc Rheometer”.

The vulcanized test plates were examined with an Instron 1122 Universal Testing Instrument with a draft of 50 mm / min. The test rods were dumbbell shaped according to ASTM Die C and cut out parallel to the fiber direction.

The results are illustrated in Figures 1 and 2, where Figure 1 shows stress-strain curves for natural rubber reinforced with various modified cellulose fibers and with untreated fibers, respectively.

Figure 2 shows Young's module for fiber reinforced rubber as a function of the amount of cellulose fibers involved. In the figures, C = untreated cellulose fibers, ABA = cellulose fibers grafted with allyl butyl acrylate, cellulose fibers grafted with butyl acrylate and GBA = cellulose fibers grafted with crotyl butyl acrylate. All the curves in Figure 1 are plotted for a fiber concentration of 30 Pnr. The curves for modified cellulose fibers all have a similar course. First a fairly sharp peak, a certain decrease followed by a plateau area and then a second peak before the break. All the grafted fibers give the reinforced rubber better half-strength than untreated cellulose fibers. Cellulose fibers grafted with butyl acrylate provide the best reinforcement.

Young's module for an unfilled rubber is proportional to its crosslink density. For a series of fiber-filled rubber samples, Young's modulus can be considered as a relatively matte on the adhesion between the matrix and the fiber. Figure 2 shows Young's modulus as a function of fiber concentration. The results show that the adhesion between fiber and rubber is best for fibers grafted with butyl acrylate. That the adhesion between fibers grafted with allyl butyl acrylate resp. crotyl butyl acrylate and the rubber matrix are slightly worse, indicating that the linear polybythyl acrylate chains are more flexible and easily penetrate the rubber matrix. Both allyl acrylate and crotyl acrylate are partially crosslinked during graft polymerization, which is likely to affect the adhesion between the fiber and the rubber matrix. If this crosslinking can be suppressed, the adhesion for allyl resp. crotyl acrylate grafted fibers increase. '

Claims (10)

462 044 BBIENIKBAX Process for fiber reinforcement of rubber by blending discontinuous cellulosic fibers in a vulcanizable rubber mixture of natural rubber and synthetic rubber before vulcanization, characterized in that the blended cellulosic fibers are modified by graft copolymerization with at least one monomer of alkyl. or alkenyl acrylate, methacrylate or a copolymer between two or more of these monomers and with an initiator in the form of an Mns * complex. A method according to claim 1, characterized in that the blended cellulose fibers are graft copolymerized with at least one C; - C 1a alkyl acrylate, C 1 - C 1: alkenyl acrylate, C; C 12 alkyl methacrylate or C 1 - C 1: alkenyl methacrylate or a copolymer of two or more of these monomers. Process according to Claim 1 or 2, characterized in that the cellulose fibers are graft copolymerized with butyl acrylate. Process according to any one of claims 1 to 3, characterized in that modified cellulose fibers are mixed into the rubber mixture in an amount of 5 to 70 Phr (parts by weight per hundred parts of rubber), preferably 10 to 40 Phr. Rubber reinforced with discontinuous cellulosic fibers, characterized in that in a vulcanizable rubber mixture of natural rubber or synthetic rubber, cellulosic fibers which have been modified by graft copolymerization with at least one monomer of alkyl or alkenyl acrylate or methacrylate are mixed before the vulcanization between two or more of these monomers with an initiator in the form of an Mn ° * complex. 462 044 Rubber according to Claim 5, characterized in that the rubber mixture contains graft copolymerized cellulose fibers in 100 parts of rubber), 7. Rubber according to the t e c k n a t of an amount of 5 - 70 Pnr, preferably 10 - 40 Pnr. any of claims 5 or 6, that the cellulosic fibers are graft copolymerized with at least one monomer of C 1 - C 1a alkyl acrylate, C 1 - C 1, alkenyl acrylate, C; - C 1: alkyl methacrylate or "C 1 - C 1a alkenyl methacrylate or a copolymer of two or more of these monomers. 8. Rubber according to t e c k n a t of diene rubber. 9. Rubber according to t e c K n a t 10. Rubber according to Claim 4 to 7, wherein one of the claims is that the synthetic rubber is styrene but one of the claims 5 to 7, wherein the synthetic rubber is nitrile rubber. any of claims 5 - 7, characterized in that the rubber is natural rubber. k ä n n e-