FI69159B - BEHANDLING FOER ATT FOERBAETTRA IMPREGNERINGEN HOS NORMALT IMPREGNERINGSPAPPER - Google Patents

Description

This invention relates to resin-impregnated papers which are more economical to manufacture and to which the resin penetrates more rapidly and completely than before. In particular, the present invention relates to a resin impregnation paper having reduced bulk, reduced resin penetration times and increased resin uptake, and a method of making an improved impregnation paper.

Impregnation paper is designed to be impregnated with resin. Several sheets of resin-impregnated paper are converted to laminate by joining and curing in a moon-15 press. For example, conventional decorative laminates include printed and coating sheets impregnated with melamine formaldehyde resin and combined with a plurality of core sheets impregnated with phenol-formaldehyde. In a heated press, the multilayer composition is converted to a monolithic panel by polymerization and crosslinking of the resins.

To satisfactorily accomplish this task, the impregnating paper must have a certain specific combination of carefully controlled properties. Above all, the 25 square meter weight must be controlled within strict specifications. This property must be monitored not only across the roller and through the roller but also on a 2/5 --- 5.0 cm ^ scale. The latter property is commonly referred to as the formation of the paper and is judged by the transparency of light through the sheet.

In this case, thin spots transmit more light than heavier clumps and lumps of fiber. In good impregnated paper, this transparency should have a low contrast, a slight difference in light transmission between the darkest and 35 lightest spots.

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Good impregnation sheets are also relatively clean, with no significant bundles of fibers or non-fibrous pieces of wood. Such substances cause non-uniformities in the structure, providing surface roughness and stress 5 concentration points. Such a substance is not easily impregnated with a resin and thus can become the starting point for bubbling.

However, important properties of impregnation papers are those that control the rate of resin absorption and spread throughout the sheet. These velocities depend on the size and number of cavities, i.e., pores, between the fibers of the sheet. Two specific terms are used for these properties: "saturability" and "penetrability".

15 Saturation describes the paper-related properties that control the dynamic, short-lived phenomenon associated with resin absorption. It includes all the properties of the sheet that control the amount of resin received between the contact of the sheet with the resin and the removal of excess resin. Due to the shortness of the time interval in question, only the larger pores of the sheet play a significant role in determining the saturation.

Penetration describes the properties of the sheet that control the distribution of resin in the sheet as equilibrium is approached. Penetrability encompasses those sheet-related properties that cause the resin absorbed by the larger pores of the paper to migrate to the smaller diameter pores and spread throughout the paper. This process 30 begins when the resin first contacts the sheet and continues until the resin has solidified in the press. The number and size distribution of smaller pores play a significant role in determining penetration.

Since both of these properties are very complex and can only be partially explained, properties that are easier to measure in practical papermaking are needed to guide the manufacturing process. Sight-density, or its equivalent, bulkiness, is a frequently used feature. Since the density of the papermaking fibers is relatively constant, the differences in the apparent density of the sheet 5 and the density of the fibers are an indication of the total volume of the pores.

Paper with a low apparent density (high fluff) has a large total pore volume, i. a lot of Large diameter pores and for this reason such pape-10 has a high saturation. On the contrary, a sheet with a high apparent density has a lot of small pores.

This results in lower saturation and higher penetrability. The apparent density of the sheet is usually controlled by increasing or decreasing the degree of pulp purification and / or compression and calendering.

In practice, it has been found advisable to use a paper base consisting of a mixture of softwood and hardwood pulp. Shorter, thinner hardwood fibers make it easier to produce paper with the required uniformity in sheet-20 formation. Because hardwood fibers are smaller, their use results in a larger number of smaller-sized pores that promote penetration. Pine fibers are necessary to give the sheet sufficient strength to be treated in a paper machine and with a resin in the impregnation operation. Pine fiber, which is larger and stiffer, tends to give the sheet fluff and thus improve saturation.

When making panels (sheets) from resin-impregnated papers, it has been found necessary to use sufficient resin to ensure that, after compression, all inter-fiber cavities are filled with resin. If this is not achieved, the physical properties of the panels and the water absorption properties will deteriorate.

Since the resin is more expensive than a sane volume of paper fiber, it is recommended to estimate the amount of resin used. Impregnation papers with high penetrations of 4,69,159 are therefore preferred. In these, the capillary forces ensure that all the finest pores are wetted by the resin and thus the microscopic cavities are eliminated.

U.S. Patent 3,827,934 discloses a process for making a high strength, high yield hardwood pulp comprising a modification of an alkaline chemical pulping treatment followed by mechanical treatment of the pulp to cause defibering along the fibrous surfaces without substantially breaking the fibers. The impregnation sheet made of high-yield hardwood pulp absorbed the resin at a rate comparable to that of a conventional sheet containing hardwood and pine pulp.

U.S. Patent 4,060,450 discloses a high-yield impregnation paper characterized by a high-yield hardwood component of 65% or more or a low-yield softwood component of 35% or less. This patent further mentions that the paper contains 8-15% lignin, which must be primarily hardwood lignin, to avoid rapid deterioration of the tools. The described impregnating paper does not have the desired properties, namely reduced fluff and reduced resin penetration times and resin uptake over conventional impregnation sheets containing lower lignin contents.

It is therefore a general object of the present invention to provide a resin impregnating paper having improved permeability made from hardwood or softwood pulps or mixtures thereof produced by alkaline cooking processes and having reduced fluff, reduced resin penetration time and increased resin uptake. in a certain

With Williams' slowness. The invention is characterized in that in the improvement the paper incorporates at least 10% by weight of pulps subjected to a first mechanical treatment to increase the pulp from a lower consistency of less than 20% to a higher consistency of 20-60% and further subjected to a second mechanical treatment of energy. at feed level h 5 69159 12.6 to 504 MJ / ton, which treatment produces twisted, sy-twisted and collapsible fibers.

It has been found that impregnating paper with exceptional permeability can be produced from various types of pulps that have been subjected to mechanical treatment at high pulp concentrations, resulting in fiber twisting, pulping, curling, and collapse. Impregnation paper made from the thus-treated pulp also has significantly fewer fiber bundles and improved dirt distribution. Impregnation papers with sufficient resin saturation and permeability can be formed by faster drying in a four-drinier, thus generally allowing a higher manufacturing speed. Alternatively, this feature may allow the production of sheets with a higher basis weight than would otherwise be possible.

Figure 1 is a graphical representation of the effect of the inventive treatment on fluff as a function of Williams inertia for untreated pulps and pulps treated at an energy level of 252 MJ / ton.

Figure 2 is a graphical representation of the effect of the inventive treatment on fluff as a function of Williams slowness for untreated pulps and pulps treated at an energy level of 504 MJ / ton.

Figure 3 is a graphical representation of the effect of the inventive treatment 25 on fluff as a function of Williams slowness for untreated pulp blends representing normal components for impregnation base paper and blends treated at an energy level of 378 MJ / ton.

Figure 4 is a graphical representation of the effect of the inventive treatment 30 on the time required for a standard resin to penetrate 5% of the sample area as a function of fluff in samples untreated pulps and pulps treated at an energy level of 504 MJ / ton.

Figure 5 is a graphical representation of the effect of the inventive treatment 35 on 5% resin penetration time as a function of fluff in untreated blends from normal paper base component pulps and blends treated at an energy level of 378 MJ / ton.

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Figure 6 is a graphical representation of the effect of adding hardwood pulp treated with the process of the invention to untreated hardwood pulp on resin penetration time.

The improved and unexpected properties of the impregnating paper of this invention result from the fact that hardwood or softwood pulp produced by an alkaline pulping process, such as a sulphate process, either continuously or in batches, or a mixture of such pulps, is subsequently treated in a mechanical step or steps. resulting in fiber twisting, co-curling, and curling.

Since the invention is based on the finding that the pulps treated by the described process result in a substantially improved resilience of the resin, the type of mechanical fiberization or the equipment used is not essential to the invention. It is essential that the mechanical defibering results in twisted, pulsed, curled and collapsed cellulosic fibers to such an extent that the impregnation paper of the present invention achieves the above-mentioned improved properties.

In order to achieve the desired effect of the mechanical treatment of the fibers, the pulp must have a relatively high consistency, i. solids content 20-60% when subjected to mechanical treatment. The preferred consistency of the pulp is 30-35%.

The following examples illustrate the invention in more detail.

Example 1 To illustrate the invention, four different types of pulps representing the normal components of the impregnation paper base were treated by the process of the invention. The pulp samples were (1) softwood pulp, (2) hardwood pulp, (3) sawdust pulp, and (4) impregnation repellent (broke) (impregnated paper base formed from a mixture of hardwood and softwood pulps and dried and then re-pulped). 7 69159 tu for mixing into fresh pulp).

The consistencies of the pulp samples ranged from 7 to 28%. Therefore, the pulp was first diluted to about 5% consistency in a low energy re-fiberizer. Temperature 5 was adjusted to 45 ° C using direct steam and samples were removed as untreated control samples.

The pulp sample slurry was then pumped to a screw press for a first processing step where the consistency was increased to 30-35%. Some twisting and 10 curling occurred. The examples used screw

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timena Sudor 100 press, but there are other acceptable ways to achieve increased consistency. Samples were removed for evaluation after screw compression.

From the screw press, the pulp was transferred by means of a feed screw directly to a twin-screw machine for further mechanical fiberization, i.e. to the second processing stage. In the examples, the device described in Swedish Patents 210,862 (July 1967) and 20,314,288 (November 1969) was used as the double screw device. The purpose of this mechanical processing step is to twist, compress, curl, knead and shear the pulp between very spaced, counter-rotating, toothed screws without actually further shortening the fibers. Each pulp sample was treated with three different energy inputs in this second treatment step. Energy feeds corresponded to approximately 252, 540 and 504 MJ / tonne. After treatment, the pulp was immediately immersed in 25 ° C water to cool the pulp. Actual operating conditions 30 are given in Table I below.

Example 2

A series of standard hand sheets were prepared to determine the effect of the process of the invention on the normal strength properties of the pulps. A large number of 35 x 25 cm hand sheets were also prepared for review by Williams 8 69159

Penetrescopella. The pulp samples of Example 1 were prepared on a 23 kg Valley cholester and the batch in each case was 2500 g of oven-dried pulp diluted to 90 liters, giving a consistency of 2.77% in the cholester. The normal procedure was to set the pH 7.0 in a cholester to produce standard sheets with zero minute chanting (grinding) after determining slowness. The pulp was then chanterized to achieve slownesses of 20, 30, and 70 s.

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Standard hand sheets were made at all levels of impact. Fifteen 25 x 30 cm heavy sheets of 200 g / m were made with both 20 and 30 second Williams inertia on a Williams sheet mold. The heavy sheets were pressed and then dried individually in an electrically heated plate dryer. The results (interpolated to a 25-second Williams inertia) for standard hand sheets are shown in Table II below.

The process according to the invention generally caused a decrease in fluff, a decrease and an increase in tensile strength in all masses, and in elongation and fracture energy at a constant inertia. A particular, most significant effect of the process according to the invention is the large reduction in the fluff of the sheets made from their own pulps with a given level of inertia. On the other hand, at a certain fluffiness, the inertia (i.e., drying resistance) is lower for the treated pulps. This effect is quite evident in Figures 1, 2 and 3.

Example 3

All resin penetration values were determined on 20 25 x 30 cm hand sheets with a basis weight in the range of 200-220 g / m 2. The instrument used for this study was a Williams Penetrescope, which determined ai & a during which the standard resin penetrated 5% through the sample area and 95% through the sample area. This instrument 25 measures the saturability and permeability of the combination because an excess of resin is present throughout the test. The shorter the Penetrescope time, the easier it is for the sheet to absorb the resin. The percentage uptake of the resin was also determined by freezing the sample at a transparency level of 5% in liquid nitrogen and comparing it to the non-penetrating sheet. The resin used for this review was phenol-formaldehyde resin with 71.4% solids. It was undiluted and had a viscosity at 23 ° C of 180-205 centipoise. The results with a 25-second Williams inertia are shown in Table III.

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Table II

Effect on hand sheet properties 25 s at Williams inertia (60 g / m square weight) 3 Pulp sample · Flour- Fepä- Punch- Fold- Bulk- Tensile- Elongation > new spring strength cm / 100 M kJ / m2 min. measure g _number_

Softwood ma s s a 10 "Untreated - carpet 21.4 173 55 737 1.89 76 2.9 101

First stage 23.5 165 56 583 1.83 78 2.8 92

Other '252) 21.1 176 54 564 · 1.84 77 3 1 103 ^ if®i! 18 '° 199 44 337 1 85 64 3.0 86 (504) 21.8 193 56 711 1.77 76 3.5 120

Hardwood pulp Untreated 6.9 102 24 12 1.84 46 2 3 50

First stage 10.8 97 26 14 1.73 44 3 ^ 0 69 vaEe1 S 7 * ° 96 23 14 ^ 63 39 3.6 80 ™ 3> 2 105 26 19 i'59 44 v 65 <5 <Μ) s, S 87 18 7 1.67 34 3.4 71

Sawdust 20 Untreated 9.0 73 15 7 1.77 31 2.0 34

First stage 10.3 74 17 8 1.69 34 2.6 48 ΙϋΒ? 1 (378) 1 * 5 ”Z9 19} ·« 37 2 7 59 504 l'1 77 17 7 1968 31 2.6 44 '' 6.2 74 16 8 1.64 32 2.9 55

Scrap x 25 Untreated 2.0 121 28 16 1.76 50 2.7 61

First stage 4.3 97 26 14 1 73 46 2.9 63

Second '252) 2,2 114 29 27 1.61 46 3 3 78 step (594) 3 <0 108 22 13 3 65 40 3% 71 (504) 4.1 93 20 8 1.69 35 3.4 63 30 Mixtures stx Handle- 5.0 115 28 19 1179 49 2.4 48

Second (378) 3.8 110 26 25 1.69 47 3 0 76 step '* x Rejection mass values 50 s at Williams inertia 35 set 60-65% hardwood pulp, 8-12% softwood pulp, 8-12% Sahaj auhc pulp, 10 -20% scrap mass 12,691 59

Table III

Effect on swell and resin penetration properties 25 s 2 5 Williams slow on heavy sheets (212 g / m)

Williams penetrescope felt side_

Pulp Energy _25 s at a slowness of 10 samples MJ / ton Grinding- BuUdci Penetration- Penetration- Resin time, min cm / g darkening uptake time, s time, s%

Soft wood Untreated 21.4 2.07 16.0 52.0 57.7 1c First stage 23.5 2.01 12.2 43.8

Second stage 252 21.1 1.78 17.1 79.8 389 18.0 1.84 10.1 38.2 544 21.8 1.72 13.8 60.9 38.8

Hardwood pulp Untreated 6.9 1.94 20.5 48.4 62.5

First stage 10.8 1.86 16.1 36.2

Second stage 259 7.0 1.70 9.4 21.7 396 3.2 1.70 4.2 11.5 533 8.5 1.68 4.6 15.3 46.0

Sawdust -c mass_ Untreated 9.0 1.86 10.9 38.6 49.5

First stage 10.3 1.85 11.2 41.1

Second stage 230 5.5 1.69 7.1 24.1 360 5.7 1.77 4.4 20.1 445 6.2 1.71 4.9 14.5 44.8 30 Freezing x Untreated 2, 0 1.94 16.8 40.5 57.5

First stage 4.3 1.83 12.3 33.1

Second stage 252 2.2 1.62 19.0 32.1 367 3.0 1.72 6.9 15.5 - 511 4.1 1.68 9.0 16.5 52.0 3 5 years

Mixture I 6.6 1.94 15.8 35.7 59.2

Mixture II ** 378 4.0 1.71 8.8 21.5 53.0 x Scrap mass values are 50 s with Williams slowness xx Mixtures are: 60-65% hardwood pulp, 8-12% softwood pulp 10-20% scrap pulp, 8-12% sawdust pulp i! 13,691 59

Table III and Figures 4 and 5 show that the penetration time of the resin is greatly reduced by treatment in all pulps except softwood pulp. The softwood pulp shows some decrease in the resin penetration time, although not as large as that found in other pulps.

Other advantages of the impregnating paper of this invention include reduced fiber bundles and decomposed dirt. In the case of hardwood pulp, sawdust and scrap samples, no fiber bundles remained with even a small energy input after 10 treatments, and the resulting hand sheets were very clean in appearance. Softwood pulp was apparently more difficult to handle; and although a significant reduction in fiber bundles occurred with low energy feed, it required the highest feed energy level (504 MJ / ton) to remove most of the fiber bundles.

The improved impregnation paper of the present invention can be made from pulps selected from the group consisting of softwood pulp, sawdust pulp, hardwood and impregnation scrap, and mixtures thereof. Paper treated as described and having the described fiber properties is less fluffy and therefore has a higher density, reduced resin penetration time and reduced resin uptake by a given Williams 25 slowness, in addition to reduced fiber bundles and improved dirt dispersion. .

Example 4

In order to determine how many fibers treated according to the invention should be present in order to cause a significant improvement in the impregnation properties of the impregnated final product, a series of blends of treated and untreated hardwood pulps were prepared. From these mixtures, hand sheets containing 0, 5, 10, 20, 40, 80 and 100% of the treated pulp were prepared.

35 Resin penetration times were determined with Williams Penetrescopel and phenolic resin with 59% solids. The results are given in Table IV and Figure 6.

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Table IV

Resin Penetration Times from Williams Penetrescope 5% Resin Penetration Time 95% Resin Penetration Time_Breaking Time_ 5 „„ 95% 95% ^ e would be reliable- confidence limits (s) 100% treated- 8.7 ± 0.9 7.5 - 9, 8 20.6 ± 1.1 19.1 - 22.1 95% of the treated 7.4 ± 1.1 6.0 - 8 ^ 8 18.4 ± 2.6 15 1 - 21 7 5% Icas ^ lltyä u * V 1 ° '4 7' ° - 7'9 16'5 4 M 15-3 - 17.7 80% treated- 20% treated 6.9 t 0.7 6.0 - 7.8 15.8 ± 1, 3 14.2-17.4 15 60% 40%] 8s? BSty 6.4 11.3 4.8-8.0 16.3 ± 1.7 14.3-18.5 20% process- 80% iclsi? eftyä S® - ^ «3 ~ 5 ^ 8 11.0 ± 3.9 6.0 - 16.0 100% treated 2.1 ± 0.3 1.8-2.4 5.0 ± 1, 1 3.6 to 6.3 The penetration times given in Table IV are graphically illustrated in Figure 6 and show the existence of a linear relationship between the amount of pulp treated and the penetration time of the resin. Statistically, the amount of fiber treated is necessary to give a significant difference in resin penetration time of about 10%.

Example V

To determine whether lower energy feeds (than approximately 252 MJ / ton) would produce significant changes in the pulp and final paper properties observed in the above examples, a hardwood pulp test was performed with different energy feeds up to 252 MJ / ton.

The hardwood was treated with the two-step treatment described in Example 1, except that the driving conditions in Table V were monitored.

15

Table V 6 915 9

Functional values 5 Test number 12345

Feed flow 375 375 375 375 375 g / min x

Consistency from first processing,% 30.0 29.7 29.9 28.9 28.8

Consistency from second reading,% 27.5 28.3 30.2 28.9 29.7

Energy supply for second processing, MJ / tonne 25.2 75.6 259 12.6 115 15 x Equivalent to approximately 83 tonnes / day

The pulp was divided into samples after the first treatment and the sample was then obtained after the second treatment. Several feed samples for the first treatment were taken during the experiment and this was understood as an untreated mass. Valley Beater review was performed on all eleven samples (untreated, 5 after first treatment, and 5 after second treatment) using a 360 g oven-dry pulp charge. The sheets were all made into nominally 3.0 gram sheets (25 to 150 g / m 2 oven dry); the filter paper was placed between the sheet and the polished plate before pressing and air drying in the fixing rings. The sheet review included fractional length and strength. The sheets were also tested for 5% resin penetration time using phenol-formadehyde resin. Table VI contains the results at different density levels.

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Table VI

Properties of pulp and paper by graphical interpolation with different pulps

Bu ^ kki Flour- Williams Break- 5% hart- Sample cm / 9 tusai- inertia mispi- Elongation sin tuna, min tuus boiling- 100 m% time, s 5 Control 57Ϊ ~ 2J5 ΓΓ6 ~ (untreated) ^, 00 8.0 21.8 44.0 2.5 19.6 1 »95 9.9 25.9 46.0 2.6 21 5 1.90 12.0 30.6 48.5 2.6 23.4

First treatment 2f05 4.8 16.3 39.9 3.0 16.2 2.00 6.1 18.9 43.0 3.1 18 1 10 l »95 7.9 22.0. 46.5 3.3 20.6 1.90 10.0 26.5 49.9 3.5 24.0.

The second concept - 2.05 4.3 14.9 37.5 2.5 15 0! Y, v 2.00 6.1 17 4 41.0 2.7 16 * 7 (12.6 MJ / tonne) 1.95 7.9 20.5 44 ^ 4 3.0 18 9 li90 9.6 26.5 48.0 3.2 21 * 6 15 The second concept-2.05 4.3 14.9 37.5 2.5 15 0! y, 2.00 6.1 17.4 41.0 2.7 16 * 7 (25.2 MJ / ton) if95 7.9 20.5 44.4 3.0 18.9 I190 9f6 26.5 48 .0 3.2 21.6

The second hand - 2.05 1.3 11.5 29.0 2.3 9.8 operation 2.00 3.5 14.0 31.6 2.5 11 2 20 (75.6 MJ / tonne) 1, 95 5.8 17.3 35! 8 2.9 13, 'o if1 8.0 21.4 41.2 3.3 15.2

The second concept - 2.05 1.0 11.5 29.0 2.2 110 MT / 4_ 2 * 00 3i2 · 14.0 31.6 2.3 13, '4 (115 MJ / tonne) 1.95 5 .7 17.3 35.8 26 160 M 21.4 41.2 2.8 18.4 25 Second hand- 2.05 1.0 11.5 29.0 2.9 7 6 ly_Q MT ,. ··> 2.00 3'2 14 »° 31.6 3.0 10) 0 (259 MJ / ton) ^ 95 5.3 17.3 35.8 3 ^ 2 llj8 7.5 21.4 41, 2 35 14 0 17 691 59

The pulps treated through the second stage require significantly less grinding time in Valley Beater to achieve a certain density. It is also apparent that the first stage treatment also significantly reduces the grind-5 mixing time to a certain fluff. The most striking effect from the different treatment levels is seen in the 5% penetration time of the resin. There is a dramatic decrease in resin penetration times at energy levels of 75.6 to 504 MJ / ton in treated sheets compared to untreated sheet. These results show a clear correlation between the energy supply and the resin penetration time. Thus, although a reduction in the resin penetration time can be achieved at second stage treatment levels of 12.6 to 504 MJ / ton, the preferred range is 75.6 to 259 MJ / ton.

Although the invention has been described and described above with reference to various specific materials, procedures, and examples, it is to be understood that the invention is not limited to said materials, combinations thereof, and procedures selected for the description.

Numerous variations in these details may be used, as will be apparent to those skilled in the art.

Claims (6)

18,691 59 1. Improved resin-impregnated paper made from hardwood or softwood pulps or mixtures thereof produced by alkaline cooking processes, characterized in that the paper incorporates at least 10% by weight of pulps subjected to a first mechanical treatment to increase the pulp from a lower consistency of less than 20% to a higher consistency of 20-60% and in addition a higher consistency wood pulp is subjected to a second mechanical treatment at an energy supply level of 12.6-504 Mj / ton, which treatment produces twisted, pulsed, crimped and collapsible fibers . Paper according to Claim 1, characterized in that the wood pulp is a softwood pulp consisting of pine or sawdust pulp or a mixture thereof. Paper according to Claim 1, characterized in that the wood pulp has an impregnable waste pulp. Paper according to Claim 1, characterized in that the wood pulp contains 60-65% of hardwood pulp, 8-12% of softwood pulp, 8-12% of sawdust pulp and 10-20% of impregnable waste pulp. Paper according to Claim 1, characterized in that the consistency of the wood pulp is increased from 30% to 35%. Paper according to Claim 1, characterized in that the amount of energy supplied in the second mechanical treatment of the pulp having a higher consistency is from 75.6 to 259 MJ / ton. of